More bodies thrown into mass graves were discovered yesterday as the death toll from a mutiny among border guards in Bangladesh rose to at least 75, with dozens of officers still missing.

Firefighters in Dhaka, the capital, said at least nine more bodies had been found in two shallow graves at the border guards' headquarters compound. Among the dead was the group's commanding officer, Major-General Shakil Ahmed.

Widespread searches were under way, both for more remains and for mutinous guards who have dressed in civilian clothes and fled their barracks. "We think there are more bodies," said a firefighter, Sheikh Mohammad Shahjalal.

The border guards, known officially as the Bangladesh Rifles (BDR), launched a two-day mutiny last week following months of simmering complaints over pay and conditions.

The 40,000-strong unit said it had long been treated worse than regular troops, and complained that its officers were not drawn from its own ranks. The guards also complained that they were ineligible for peacekeeping duties with the UN, a high-paying mission much coveted in a country struggling with poverty.

It appears the revolt had been planned for some time, and was timed to take place when officers from across the country were attending a meeting in the capital. Witnesses told how the guards, armed with automatic weapons, burst in on the officers and lined them up before spraying them with gunfire. The bodies were then thrown into quickly dug graves or stuffed into drains around the compound.

The mutiny has proved a serious test for Bangladesh's newly elected prime minister, Sheikh Hasina. She was sworn in two months ago after an election in December ended two years of emergency rule by an interim, military-backed government.

Having pleaded with the mutinous guards to lay down their arms and avoid unnecessary bloodshed, she offered an amnesty to those who surrendered, but vowed that those responsible for murder would not escape justice.

Rebellion and insurrection among the armed forces is nothing new in Bangladesh. The prime minister, serving her second term, is the daughter of Sheikh Mujibur Rahman, the country's independence leader and its first head of state, who was shot dead by military officers in a 1975 coup. His wife and three sons were also killed, but Hasina was out of the country at the time.

"It's a setback for Sheikh Hasina's new government. It's now a test for her how she handles the military," said Ataur Rahman, a political analyst. "This tragic event will force her to divert attention from consolidating democracy and boosting the economy to tackling the challenges of national security."

Bangladesh's army chief, General Moeen U Ahmed, met Hasina at her Dhaka home on Friday evening, and later promised that his troops would back her civilian leadership. "It's a national crisis. The military will stand by the government," he said.

Troops are still scouring Bangladesh for those guards involved in the mutiny, with roadblocks and checks on the country's numerous ferries.

The government has set up a committee to investigate the causes of the mutiny and establish why it had not been anticipated. Representatives from the army are to be included on the committee. A special tribunal will try those responsible for the killings.