Sudan ? Pro-government militiamen have stepped up attacks on villages in Darfur, killing dozens of people in recent days, international observers in the wartorn Sudanese region said.

During one raid on a Darfur village, janjaweed militiamen – backed by government troops – forced children into a thatched hut, then set it ablaze, killing parents who tried to rescue the children, rebels said.

The U.N. said it was looking into reports that four children and two adults were killed in a raid on the village of Madu but could not confirm whether the children were burned alive.

The Sudanese army denied any connection to janjaweed attacks, saying the claims were politically motivated.

Violence has marred the vast arid Darfur region since 2003, when rebels from ethnic African tribes took up arms against the Arab-dominated central government. Khartoum is blamed for having unleashed the janjaweed militias in response; they are accused of many of the atrocities in a conflict that has killed some 200,000 people and chased 2.5 million from their homes.