Arab militias chained civilians together and set them on fire in Sudan's western Darfur (search) region, where tens of thousands have been killed in a 17-month conflict, according to a report by an African Union (search) monitoring team.

The immolation came during a July 3 attack on the village of Suleia was attacked July 3 by the pro-government militias known as the Janjaweed (search), the monitoring team said in its report.

"The attackers looted the market and killed civilians, in some cases, by chaining them and burning them alive," according to the report, a copy of which was obtained by The Associated Press on Thursday.

It did not say how many people were killed.

The report, which was not signed but was written on African Union letterhead, also said the village of Ehada "had been burnt and deserted except for a few men. ... an unwarranted and unprovoked attack on the civilian population by the Janjaweed."

African Union officials were not immediately available for comment on the report.

The African Union monitors are supposed to be observing a cease-fire signed in April between the government and the region's two black rebel groups. But fighting has continued in Darfur, where militias drawn mostly from nomadic Arab tribes have launched a brutal campaign to drive out black farmers.

The United Nations estimates up to 30,000 people have been killed in Darfur, more than a million driven from their homes, and some 2.2 million left in urgent need of food and other aid. The U.S. Congress has labeled the atrocities genocide.

The conflict stems from long-standing tensions between nomadic Arab tribes and their African neighbors over dwindling water and farmland. Tensions exploded into violence in February 2003, when the two rebel groups took up arms over what they regard as unjust treatment by the government.

The European Union (search), the United States and humanitarian groups accuse the Sudanese government of backing the Janjaweed with vehicles, helicopters and airplanes — a claim Khartoum denies.

The monitoring team originally investigated the attack at Suleia after a complaint by the Sudanese government against the two rebels groups, the Sudanese Liberation Army and the Justice for Equality Movement. But the monitoring team found that the attack was carried out by the Janjaweed.