MOGADISHU, Somalia - Three battalions of peacekeepers from Uganda and Nigeria will be airlifted as soon as possible into Somalia amid rising violence that threatens the government's grip on power, an African Union official said yesterday.

Somalian Prime Minister Ali Mohamed Gedi began imposing martial law in areas his government controls, beginning with a curfew Tuesday night in the southern town of Baidoa.

Gedi warned that remnants of an ousted Islamic movement had returned to towns and cities and were planning to try to further destabilize the lawless country.

"From now on, martial law would be implemented across government-controlled areas, starting with Baidoa," Gedi said late Tuesday.

Since last month, when Somalian government troops with crucial support from Ethiopian soldiers, tanks and war planes ousted the Council of Islamic Courts, factional violence has again become a feature of life in the capital, Mogadishu.

Ethiopia says it does not have the resources to stay as a peacekeeping force and has begun withdrawing, presenting the possibility of a dangerous power vacuum.

In neighboring Ethiopia, a senior African Union official said yesterday that three battalions of peacekeepers from Uganda and Nigeria were ready to be deployed in Somalia and would be airlifted in as soon as possible.

The African Union was pressing ahead with its peacekeeping mission to Somalia despite securing only half the 8,000 troops needed at a key summit of African leaders that ended Tuesday. So far, five nations - Uganda, Nigeria, Malawi, Burundi and Ghana - have pledged about 4,000 troops.

The African Union official said securing the 8,000 troops would not be difficult. The main challenge, he said, was raising the estimated $34 million a month to pay for the mission.