MOGADISHU, Somalia (AP) _ Militiamen loyal to warlord Mohamed Farah Aidid reportedly killed 10 Somalis and seized 20 foreign aid workers during an assault on one of Somalia's largest cities, witnesses said Monday.

The report contradicted earlier claims that Aidid's forces met no resistance Sunday when they captured Baidoa from supporters of rival warlord Ali Mahdi Mohamed.

Mahdi threatened Monday to attack the town if Aidid's men don't withdraw within 48 hours.

The U.N. Development Program said it was trying to get the 20 foreign aid workers freed, and had sought permission for an aircraft to fly to Baidoa to evacuate them to neighboring Kenya.

``As far as we know, they are all safe, but they are not allowed to communicate with their head offices,'' said an agency official in Nairobi, Kenya, who spoke on condition of anonymity.

Aidid, who controls southern Mogadishu, led a convoy of 25 to 30 trucks mounted with weapons Sunday to capture Baidoa, 130 miles northwest of Mogadishu. It was one of Aidid's biggest military moves since he was ousted from the area in 1993.

Baidoa's population is about 300,000.

Ahmed Tahir Abdi, an Aidid supporter, said in Mogadishu that the general's militia disarmed guards protecting aid agencies and confiscated communication equipment.

The U.N. official said 11 of the workers are employees of U.N. agencies and the rest work for private aid organizations. Eighteen of the workers were reported confined in the compound of the U.N. Children's Fund and two at a building owned by CARE International.

Witnesses arriving in Mogadishu from Baidoa said at least 10 people were killed when militiamen belonging to the Rahanweyn clan tried to fight off Aidid's militia.

Aidid, who controls most of southern Mogadishu, had his supporters name him Somalia's president in June, shortly after he lost the leadership of the Somali National Alliance faction to his former financier, Osman Ato.

Baidoa was controlled by the Rahanweyn clan, which supports Mahdi, who controls northern Mogadishu and also claims to be president of Somalia.

On Monday, Mahdi described Aidid's takeover as ``provocative'' and charged ``the responsibility of a catastrophic war in Somalia will rest on Aidid's shoulders.''

Since claiming to be president, Aidid has been trying to consolidate his position.

He has formed a government unilaterally and ordered individuals to surrender firearms to his militias. On Saturday, Aidid gave aid agencies 21 days to register with his government at fees ranging from $100 for foreign groups and $80 for local ones.