Hassan was walking through town one afternoon, killing time, when he bumped into a friend, near the football stadium. "I've got some spray paint," said the friend. They agreed to meet later that night, by the bakery.

They met at 12, and walked a short way into a residential quarter. At one end of a long, narrow street, they started spraying, using black and red paint. "Down with colonial occupation" and "Viva Polisario", they wrote, in letters two feet high. They worked quickly but carefully; they wanted their work to be legible, not artistic. They covered one hundred metres of the street with slogans, and by 12.10 they had finished. On a high, they celebrated with a coffee in the nearby Café Alaska.

That was in May 2007. In October, Hassan found himself in a cell in the police station, naked, watching another man being raped with a bottle, by police. If he didn't confess, he was told, the same would be done to him.

He confessed – to a crime he says he knew nothing about, the torching of a police car. But later, when he was presented to the chief of police, he refused to repeat his confession, and he was taken back to the cells. This time, he was given the faroj, or "roast chicken", – a "well known torture in the region", I'm told. This consisted of being placed in a foetal position with his feet bound and his arms bound around his legs. Then a pole was pushed behind his knees, and the pole was lifted so that he swung from it, upside down, like a chicken roasting on a spit. For three days, he says, he was tortured, beaten and insulted, though his interrogators took care not to scar him. He was shown photos of the graffiti he had painted, and made write out the same slogans on paper, so that his writing could be compared.

Brought to trial, he entered the courtroom making the victory sign and shouting, "No place for colonial justice!" He threatened to go on hunger strike. The judge replied, "you can suffocate yourself if you want; it won't do you any good". He was found guilty (on the charge of torching the police car) and sentenced to ten months, which he completed in August.

"I'm sure, after your departure, I'll be arrested again," he says, and smiles. There is a twinkle in his eye.

Hassan Eddah is a 22 year old Saharawi, from the country once known as Spanish Sahara, now known as Western Sahara. That, at least, is how it's known to those who recognise it; to the rest, it is simply the southern provinces of Morocco. It is a vast stretch of desert, with a handful of towns, a rich seam of phosphate, some of the richest fishing waters in the world and, possibly, off-shore oil. The Saharawis are the native people, nomadic tribes of Arab and Berber origin; though they are nomads no longer, for they have nowhere to go.

There are perhaps 400,000 of them (no one has properly counted). Some live here, in Laayoune, the small, squat, modern Western Saharan capital, and the handful of other towns in Moroccan-controlled territory. Many, though, are stuck in refugee camps across the border in Algeria, where the leadership of the Saharawi liberation movement, Polisario, is based. Hassan has four older brothers in the camps; the youngest left to join Polisario in 1995, and Hassan has not seen any of them since. I ask him will he join them.

"I want to struggle from here," he says. "I don't want to leave this land to the colonists."

His struggle is a simple one. He is not a revolutionary; his weapons are spray paint and the Polisario flag. "I'm just a simple militant," he says. "I call for self-determination."

I ask him what are his personal hopes for the future, what are his ambitions? "The only thing I see is our flag on this land."

This land is Africa's last colony. Situated just south of Morocco, on Africa's north west coast, it was a colony of Spain until 1975, when domestic difficulties and international pressure forced Spain to withdraw. Independence beckoned for the Saharawis, supported by a decision of the United Nations' International Court of Justice, which ruled they had the right to self determination.

Instead, Morocco invaded. And what an invasion! Morocco's King Hassan II called on his people to mobilise, and 350,000 Moroccan civilians marched south to claim the Sahara as theirs.

There are photos of this march all along the corridors of our hotel in Laayoune: glorious images of a massive popular movement; a vast parade of poor rural people, swathed in desert robes, carrying the red flag of Morocco, marching, camping, riding in packed trucks. This was the "Green March", so called because it was carried out in the name of Islam (though the Saharawis, too, are Muslim).

The Green March has become the defining expression of Moroccan sovereignty. It was, however, largely a public relations exercise. The marchers barely entered Western Sahara, came nowhere near any of the towns, camped for three days, and went home.

Yet Spain bowed to Moroccan pressure, and signed an agreement with Morocco and with Mauritania (the country to the south), dividing Western Sahara between them. Both countries sent their armies in. Perhaps a hundred thousand Saharawis fled east into Algeria, and their liberation movement, the Polisario Front, declared a government in exile.

Mauritania eventually withdrew, but Morocco cemented its control over the Sahara by building a wall, a 1,600 kilometre long berm of sand, securing the territory against Polisario incursions. One hundred thousand Moroccan soldiers are stationed along the berm today.

The Saharawis that remained were effectively herded off the land, into the towns. There was severe political repression, and hundreds "disappeared", arrested and detained in secret prisons. In the most extreme cases, various people tell us, the Moroccan army threw people from helicopters or buried them alive, as was reportedly done at that time by various state security services in Latin America. The families of the disappeared were told nothing about where and how they were.

Aminatou Haidar was 20 years old when she was arrested, in 1987. She was involved in planning a demonstration to call for self determination and human rights. At half past three in the morning, the police took her from her parents' home. She was interrogated and tortured for three weeks, she says. She was beaten, bound, placed in stress positions and given electricity. Then, she was transferred to another prison, where she spent three and a half years in a cell measuring 10 feet by 10 feet, sharing it with nine other women. They were blindfolded constantly and not allowed to talk.

"We were totally isolated from the outside world. Our families assumed we were dead. There was no legal process at all. They treated us like animals, in cages."

But the women around her gave her strength. Some had children, and their fortitude impressed her. She was young, and she had, after all, expected to be arrested. "My uncle and my cousin had been 'disappeared'. So I was psychologically prepared.

"But the second time was harder."

A ceasefire between Morocco and Polisario in 1991 led to the release of the "disappeared", and Aminatou Haidar returned to her family and her studies. But she also returned to her activism, becoming a leading member of the Collective of Saharawi Human Rights Defenders (Codesa). In 2005, she was arrested again. This time, she was put through what she says was a sham legal process, charged with forming a criminal gang, convicted and imprisoned.

"I had children by then. I was always worrying about them: are they eating, are they sleeping, are they well? Even though I spent just seven months detained, and despite the fact that I had visits from my family, it was harder."

At its nadir, conditions were so bad that she and her fellow political prisoners went on hunger strike, demanding better treatment. Some of her colleagues were not allowed family visits, and Aminatou Haidar decided to forsake her own family visits in sympathy.

"My children pleaded with me to stop. But we took a collective decision, and I couldn't."

The strike lasted 51 days. They won some of their demands, and Aminatou Haidar was released after seven months.

Aminatou Haidar tells me her story some time in the early hours, in the house of one of her colleagues in Codesa, in Laayoune. There is no secrecy about the meeting – everybody knows they are being followed anyway. But because it is Ramadan, the Muslim period of fasting, people prefer to meet late and talk into the night. As we talk, a colleague laboriously prepares a very sweet green tea, which simmers on a charcoal burner sitting on the carpet, and is then poured into small glasses, emptied back into the pot and poured again, over and over until it acquires a small froth. "We are orthodox," he jokes. "You have to respect the rules." Until 3am, Aminatou Haidar and her colleagues tell us their own stories; of their concerns for human rights in the region. Though Saharawi self-determination is their goal, they talk much of organising civil society in Western Sahara, and of alliances with human rights organisations in Morocco, to push for democracy and greater freedom of expression and organisation. Then they go home to eat with their families, before fasting begins at sunrise.

The next morning, Aminatou Haidar takes us for a drive. The white Peugeot 205 that always follows us is behind, as usual, but when she stops to show us the former prison where she was held upon her arrest in 2005 (now disused), we acquire a second escort, a police car. Two men squat on a corner across the street, watching. Haidar points them out, smiling. She walks down the street for a photograph, and a third escort arrives: a police van appears on a parallel road and turns onto our road and crawls past us.

If there has been one beneficial consequence of Aminatou Haidar's imprisonment, it is that she has become a figurehead for the Western Saharan human rights movement. In November, she will fly to Washington to receive the prestigious Robert F Kennedy Human Rights Award. And she, along with other human rights defenders here, is supported by Front Line, the Irish-based charity that works to protect such defenders internationally.

This status gives her a level of protection, and a confidence that the authorities will be careful not to overstep the mark with her. Even still, she says, she is routinely harassed.

Gradually, the week starts to blur. We are seated on cushions on the carpeted floor of someone's living room, and an elderly woman is telling of having been abducted, aged 24, leaving her five-month old daughter behind. Her daughter died. The woman was imprisoned for… was it 16 years? Or was that the lawyer? An 18 year old boy is showing us the swelling on his thigh where, he says, he was beaten by the police, yesterday, for being a Saharawi nationalist. We leave our hotel, and the white Peugeot 205 is waiting, parked further up the road. We are seated on cushions on the carpeted floor of someone's living room, hungry, while someone is telling a story of harassment and beatings and torture, and in the kitchen the women are preparing the meal to break the fast. We are eating soup and unleavened bread, and swapping mobile-phone photos of our children. A woman describes sharing a cell with eight others for five years, without exercise or washing facilities. The only time they could talk was when the guard on their cell door took a break because the smell from the cell was so nauseating. They tell us these stories, carefully and politely, and then invite us to eat with them. We sit cross legged on the floor, eating with our hands, and the conversation turns to laughter.

We drive east through the desert. Two checkpoints leaving Laayoune. Polite, but slow; forced to wait at the side of the road. We drive for two hours across flat, dusty, grey-brown scrub. A water truck sucks rainwater from a large puddle, to sell it in the town. Some goats stretch to nibble at bushes and acacia trees. Camels loll across the road. More checkpoints, more questions. The entrance to Smara: a tiny town half way to the Moroccan berm, home to a UN camp ("no pain, no gain" says a sign there, incongruously); a small, squalid shanty town; a dilapidated main street with an internet café and some tired looking shops; and a straggling suburb of half-built houses. (The fashion here is to build one storey at a time, and move into the completed section while saving to build higher.) There is a meeting of the Saharawi Committee for Human Rights in Smara. A long introduction. A detailed story of a "disappearance". Photos of young men beaten last week, and the men themselves showing what remains of their scars and bruises. An elaborate lunch, prepared just for us (it is daytime, so they will not break fast). I ask 18-year-old Lakhtour Nafaa, who has told me how, yesterday, he was arrested, beaten and threatened that he would be raped with a bottle, if he will see independence in his lifetime.

"Only God knows," he says. Would he like to join Polisario? "No. I will stay here till independence." Why?

"Because this is our land."

One evening, the photographer thinks that his laptop has been opened while we were out during the day. We assume our rooms are being searched. Our security "companions" are present whenever we step outside the hotel. On our final morning, one of the team notices some graffiti on his bag. "Accomplish unfortunately", it says, in blue biro; it seems an awkward translation from the French: accompli, malheureusement. In the lobby, we speculate on its meaning: a warning; a simple sign of frustration; a wry note of acknowledgement? Hassan II looks on from the painting. His son, King Mohamed VI, looks down from a framed portrait. Outside, our security tail is waiting. Whose land is it? What has been accomplished? The Saharawi people are waiting for answers.

The Moroccan Embassy in Dublin declined to respond to queries from the Sunday Tribune relating to the key allegations cited above.

Front Line, the International Foundation for the Protection of Human Rights Defenders, was established in 2001 to provide human rights defenders at risk with round the clock practical support so that they can continue their work safely.

Human rights defenders are people who make extraordinary sacrifices, often putting their lives at risk defending the rights of others. They are people who are either on the move or on the run and they are the people who change society. They are most at risk when they touch powerful interests demanding accountability or full economic and social rights.

Front Line provides a fast, flexible 24-hour emergency response that contributes to the protection of HRD at immediate risk. This response consists of direct interventions, international advocacy, grant support and emergency relocation. Front Line operates in English, French, Spanish, Arabic and Russian, and the organisation delivers regional and international training in personal security, risk assessment and IT?security to help them manage their security.

To date Front Line has taken up the cases of more than 800 individual human rights defenders at risk, from over 100 countries. This is the second of five articles on Front Line defenders around the world which will appear in the Sunday Tribune between now and December.