A group of masked men travelled around south Armagh removing posters seeking justice for Paul Quinn, the Cullyhanna youth beaten to death by Provisional IRA members in a cowshed.

Quinn's parents said they were "deeply distressed" by the attempt to stop the campaign to bring their son's killers to justice. The masked men even took down posters erected by the Quinns in the laneway leading to their home.

The posters showed a photograph of the murdered 21-year-old above the question, "Is Paul Quinn's murder on your conscience?"

Quinn's father Stephen told the Sunday Tribune: "Breege and I lay sleeping in our bed, while faceless men came in the dark of night and removed these posters just yards from our home. What sort of people are they?

"Have they no compassion nor humanity? Isn't it enough that they murdered our son. Now, it seems, they want to remove all traces of him. They are cowards, utter cowards. But we will not be bullied by men with or without balaclavas. They killed our son, what more can they do to us?"

Paul Quinn was beaten to death 18 months ago in Oram, Co Monaghan. He was lured to a farm where eight men set upon him with iron bars and nail-studded cudgels. Fourteen people from both sides of the border have been arrested and questioned about his murder.

Last weekend, several local people reported seeing a white transit van with the number plates removed driving across south Armagh. Five men, all wearing balaclavas, got out and removed the posters.

They stopped at various locations including Crossmaglen and Culloville. At one point, the van crossed the border and was followed by a supporter of the Quinns into Co Monaghan.

The Quinns said posters beside Crossmaglen police station had been taken down and the family hoped their removal might be captured on the barrack's CCTV cameras.

In the early hours of St Patrick's Day, the group of men then visited Cullyhanna where they removed posters in the village, including those at St Patrick's church and graveyard, where Quinn is buried. Breege Quinn said: "The removal of the posters wasn't spontaneous. It was an orchestrated and deliberate act. We believe it was carried out by those involved in Quinn's murder or their associates.

"It shows that some people in south Armagh are against any freedom of speech and expression. We need to hear what Sinn Féin makes of this matter."

Stephen Quinn said: "Replacing the posters will be expensive for us but it doesn't matter how much it costs, we will not be silenced. New posters will be erected soon."

Among those questioned about Quinn's death was Paudie Treanor, the former driver of Sinn Féin minister Conor Murphy. Treanor has since been charged with possessing an AK47.

Breege Quinn said the PSNI and garda investigation had been hampered by a lack of co-operation from suspects. "They are going in for questioning and sitting in silence looking at the wall," she said.