The army led by Muqtada al-Sadr, seen in 2003, is suspected of spearheading the killings of hundreds of men in Iraq. ((Pier Paolo Cito/Associated Press))

Iraqi militias are torturing and killing "hundreds" of men in a growing, systematic campaign against suspected homosexual activity that may be aided by Iraqi security forces, an international human rights group said Monday.

The bodies of several gay men were found in Baghdad's main Shia district of Sadr City earlier this year with the Arabic words for "pervert" and "puppy" — considered derogatory terms for homosexuals in Iraq — written on their chests, according to a report released Monday by Human Rights Watch.

The killings have spread to other cities and areas in the country, but remain centred on the capital, according to the report.

"The killers invade homes and pick people up in the street, witnesses and survivors said, interrogating them before murdering them to extract the names of other potential victims," the rights group said in a statement.

Reliable numbers weren't available, Human Rights Watch said, blaming a combination of the failure of authorities to investigate such crimes and the stigma preventing families from reporting the deaths. But it cited a well-informed UN official as saying in April that the death toll was probably "in the hundreds."

The Mahdi Army, a Shia militia run by radical cleric Muqtada al-Sadr, is suspected of spearheading the killings, Tom Porteous, the London director of Human Rights Watch, told CBC News on Monday.

In an interview from London, Porteous said the Mahdi army has for the most part suspended its military resistance to the U.S. presence in Iraq, but has been eager to show it still has influence over the daily lives of Iraqis.

"One theory is in order to maintain relevance and to gain publicity, they are now taking it upon themselves to run a campaign to — in the words of some preachers and some media commentators — cleanse the country of depravity, which again is being interpreted as being brought in by the foreign invasion and occupation," he said.

The report also cited several cases of so-called honour killings, in which families kill their gay relatives to avoid public shame.

'They are massacring us'

Human Rights Watch included the individual accounts of dozens of Iraqi men forced to flee their homes or the country because of a "radically new intensity" to anti-gay attacks in Iraq this year.

Among them is Atif, 27, from the Zayouna area of Baghdad, who said he fled for northern Iraq at the beginning of April.

"I call people in Baghdad and they tell me, 'Don't come back, they are massacring us. They are massacring gays here,'" the report quoted him as saying.

Another man described how four masked men, dressed in black, kidnapped his partner of 10 years in April.

"He was found in the neighbourhood the day after," the man was quoted as saying. "They had thrown his corpse in the garbage. His genitals were cut off and a piece of his throat was ripped out."

Homosexuals have been targeted throughout the Iraq war, but the killings appear to have intensified as improvements in overall security led gay men to begin going out to cafes in groups and socializing in public, according to the report.

Human Rights Watch accused authorities of doing nothing to stop the killings and warned that reflected an overall inability to protect the people.

There is no law against homosexuality in Iraq, but a spokesman for the Interior Ministry said it receives few complaints of abuse because of the secrecy and stigma attached to homosexuality in Iraqi culture.