Tamil men seeking asylum in Europe claim they were abducted, raped and tortured by government forces in Sri Lanka.

Details of the abuse of more than 50 men, which one human rights expert has described as “the most egregious and perverted that I’ve ever seen”, have been revealed by the Associated Press.

One man said he was held for 21 days in a room where he was raped 12 times, burned with cigarettes, beaten with iron rods and hung upside-down.

Most of the men said they were abducted from their homes or taken off the street before being blindfolded and driven to detention sites. The men said they were accused of working with the Tamil Tigers, and almost all were branded with marks made to look like tiger stripes.

A man shows scars on his back that he claims were inflicted by Sri Lankan security forces. Photograph: Frank Augstein/AP

Their captors often identified themselves as members of the criminal investigations department, a police unit that looks into serious crimes.

The agency conducted interviews with 20 men and reviewed 32 medical and psychological evaluations. The cases date from early 2016 to July this year and include tales of brandings, beatings, and repeated

Lt Gen Mahesh Senanayake of the Sri Lankan army denied the alleged involvement of military and police forces. “The army was not involved and … I’m sure that police also were not involved,” he said. “There’s no reason for us to do that now.”

Most of the men claimed they were sexually abused or raped, sometimes with sticks wrapped in barbed wire.

“I want the world to know what is happening in Sri Lanka,” said one 22-year-old man. “The war against Tamils hasn’t stopped.”

Piers Pigou, a South African human rights investigator who has interviewed torture survivors for the past 40 years, said: “The levels of sexual abuse being perpetuated in Sri Lanka by authorities are the most egregious and perverted that I’ve ever seen.”

One victim, who had been a member of the Tamil Tigers nearly a decade ago, said that after the war he returned to his family farm and married his high school sweetheart. Soon after his wedding, he was abducted off the street and tortured.

“They heated up iron rods and burned my back with stripes,” he told the AP. “On another occasion, they put chili powder in a bag and put the bag over my head until I passed out. They … raped me.”

After his family paid a bribe, he was freed. He had to be hospitalised for 10 days after his release and fled to England without saying goodbye to his wife.

Most of the men said they were only released after their families paid a bribe averaging 500,000 Sri Lankan rupees (£2,488). Once free, they fled the country and claimed asylum in Europe.

Ann Hannah, head of international advocacy at Freedom from Torture, which provides medical assessments to support asylum claims, told the Guardian the stories highlighted by the AP were “completely consistent with the types of abuse we’ve seen and been documenting for many years, including since the end of the conflict”.

Hannah said that, over the past five years, Sri Lanka was “by a considerable margin” the most common country of origin for torture victims seen and assessed by the organisation. In their last report on the country, 84% of torture victims were men; 71% reported sexual torture including rape.

Hannah said one of the difficulties for Sri Lankan asylum seekers was proving that the risk was ongoing even though the conflict ended in 2009. She said that, in some cases, people refused asylum in the UK had been returned to Sri Lanka, where they were abducted and tortured again.

A total of 845 people from Sri Lanka applied for asylum in the UK last year. Only 6% of those whose cases were decided last year were granted asylum or another protection visa, well below the average of about 30% for all nationalities.

“The number of referrals we’re seeing is not dropping off since the conflict,” said Hannah. “Political rhetoric about Sri Lanka being a different place, and EU trade relations being re-established due to improvements in the human rights situation, is not consistent with what we’re seeing.”

Last year, Sri Lankan authorities were called to Geneva to testify before the UN Committee Against Torture. When questioned about the alleged use of torture against suspects in police custody, Jayantha Jayasuriya, Sri Lanka’s attorney general, said it was prohibited by the country’s constitution. He also said “strict action” would be taken against perpetrators of human rights violations.

The civil war in Sri Lanka, fought between the Tamil Tigers and the government, ended in 2009 after 26 years of conflict. The UN has estimated that more than 100,000 people died in the war, including up to 40,000 civilians in its final months.

Many Tamils claim the government continues to target them and that they are treated as “second-class citizens”.