Militiamen on horseback ambushed a refugee convoy in Sudan's western region of Darfur, executing about 30 civilians, the United Nations and aid workers said Sunday.
African Union peacekeepers called to investigate were briefly taken hostage by other refugees, the U.N. reported.
The aid workers and a U.N. statement said pro-government militiamen known as janjaweed ambushed a truck Saturday outside Sirba, on a road near the border with Chad.
"Some of the passengers were shot by the attackers and others were burnt to death," the U.N. statement said.
The governor of West Darfur, where the killings occurred, blamed the attack on antigovernment rebels who he claimed were seeking "to make citizens lose confidence in the African Union."
More than 200,000 people have been killed and 2.5 million have been forced from their homes since ethnic African rebels rose up against Sudan's Arab-dominated government in 2003.
The regime in Khartoum is accused of responding by unleashing the janjaweed militias of Arab nomads, who have been blamed for most of the atrocities. Sudanese officials deny using the janjaweed.