Baghdad: Militiamen are torturing and killing gay Iraqi men in a systematic campaign that has spread from Baghdad to several other cities, a rights group said in a report.

Human Rights Watch on Monday called on the Iraqi government to act urgently to stop the abuses, warning that so-called social cleansing poses a new threat to security.

The bodies of several gay men were found in Baghdad's Shiite 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.

The New York-based advocacy group said the threats and abuses have since spread to the cities of Kirkuk, Najaf and Basra, although the practice remains concentrated in the capital.

"Murders are committed with impunity, admonitory in intent, with corpses dumped in garbage or hung as warnings on the street," the 67-page report said.

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 campaign has been largely blamed on Shiite extremists who have long targeted behaviour deemed un-Islamic.

Fliers warning homosexuals that they will be killed "unless they come back to their senses" were distributed in Sadr City earlier this year and Shiite clerics have frequently called for the "education and rehabilitation" of gays in their Friday sermons.

"The same thing that used to happen to Sunnis and Shiites is now happening to gays," said a doctor who had fled Baghdad and was interviewed for the report. The doctor, who described himself as gay, said several of his friends had been killed.

An Iraqi Interior Ministry official, speaking on condition of anonymity, acknowledged there has been a sharp escalation in attacks against gay men this year by suspected Shiite extremists.

However, he told The Associated Press that the ministry does not have numbers "because in most cases the family members themselves are either involved in the killing or prefer to keep silent, fearing shame."

The former No. 2 official at the US Embassy in Iraq, Patricia Butenis, wrote in a letter to a US congressman that reports from contacts familiar with the areas where some of the bodies were found "suggest the killings are the work of militias who believe homosexuality is a form of Western deviance that cannot be tolerated."

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

The Human Rights Watch report was based on interviews with more than 50 Iraqi men who identified themselves as gay as well as Iraqi human rights activists, journalists and doctors.