"Kirkuk right now is a tinderbox," said Hania Mufti, London director of the Middle East and North Africa division of the New York-based rights watchdog.

"US troops must stop the violence. And Patriotic Union of Kurdistanleaders should take immediate steps to halt any expulsions of Iraqi Arabs from their homes," Mufti said.

Widespread looting and destruction of property are affecting all ethnic groups in the city, while the situation outside of Kirkuk appears even more precarious, he added.

Human Rights Watch said one of its teams had documented the expulsion of Arabs living in villages south of Kirkuk, on the basis of what one official said were policy decisions by the PUK.

Since April 10, at least 40 civilians have been killed in Kirkuk, Mufti said.

Many of them appeared to have died as a result of clashes between armed civilians and the former ruling Baath Party.

According to forensic records, at least two died from close range single gunshot wounds to the head, and a third, whose hands were bound, bore lesions on the neck consistent with hanging.

Human Rights Watch said that the US and interim Iraqi authorities, including Kurdish representatives, should take steps to establish as soon as possible a mechanism to settle claims over disputed property and other assets.

In 1973, as part of the Iraqi government's policy to permanently settle Arab nomadic tribes from central and southern Iraq, families from the al-Shummar tribe were resettled in the al-Iskan area, south of Kirkuk.

They were given homes as well as agricultural land that belonged to forcibly displaced Kurds.

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