The mysterious death of an imam in Thai army custody last week has highlighted the plight of Muslim rebel suspects who say they have been tortured while detained for interrogation, Human Rights Watch said yesterday.

Torture included ear-slapping, beating with wooden and metal clubs, forced nudity, exposure to cold, electric shocks, strangulation and suffocation with plastic bags, the rights body quoted freed detainees as saying in a statement.

"Muslims in southern Thailand live in fear of the army storming in to take their men away to be tortured," Brad Adams, Asia director at the New York-based agency, said in the statement.

"The army is fighting an insurgency, but that doesn't mean soldiers can abuse people. And prosecuting troops for mistreatment could actually help calm the situation and rebuild trust with the Muslim community," Mr Adams said. But Army spokesman Colonel Acra Tiproch said only "a small faction" of Muslim detainees had been abused and then only because they "provoked" interrogators as a ploy to demonise the Buddhist state and its troops.

"Some of these suspects are well-educated and they know well how to make junior interrogators lose their patience and start beating them," he said by telephone from the Malay-speaking zone, a former sultanate annnexed by Bangkok a century ago. Nearly 3,000 people have been killed in four years of a separatist insurgency in the region, which has seen fewer attacks in the past four months.

A university think-tank cataloguing the unrest attributed the decline to the deployment of more troops by new army chief Anupong Paochinda, who took office in October, and almost daily raids on suspected targets.