EL FASHER, Sudan — African peacekeepers were searching for more than 20 members of their force still missing and feared wandering the wilderness of Darfur today after rebels overran their base in an unprecedented attack that stunned the international force.

The attack Sunday on the Haskanita base in northern Darfur illustrated the chaos in the war-torn region ahead of peace talks later this month — and the dangers that could face a bigger United Nations force due to start deploying in coming weeks.

In Sunday's attack, around 1,000 well-armed rebel gunmen overwhelmed the small Haskanita base of about 150 troops before dawn after hours of fighting, during which some of the African soldiers ran out of ammunition. The battle killed at least 10 peacekeepers in the deadliest attack on the AU force since it deployed in June 2004. The rebels retained control of the base until early Sunday, when Sudanese government troops arrived and forced them out of the area.

A group of 23 peacekeepers were still unaccounted for after the attack and were believed to be wandering around the barren area near Haskanita, AU officials in El Fasher, capital of North Darfur state, said.