MOGADISHU, Somalia - A roadside bomb struck a convoy carrying African Union peacekeepers Wednesday, killing four peacekeepers in one of the deadliest attacks on the troops since they arrived in March, authorities said.

The attack occurred just weeks after the Somali government declared victory over Islamic insurgents who have vowed to launch an Iraq-style guerrilla war unless the country becomes an Islamic state. The capital, Mogadishu, has been relatively calm since then, with sporadic bursts of deadly violence.

"Four of our solders were killed on the spot by the roadside bomb in north Mogadishu," said Capt. Paddy Ankunda, a spokesman for the AU force.

Uganda has about 1,400 troops in Somalia, officially as the vanguard of a larger African Union peacekeeping force although so far no other countries have sent reinforcements.

The most recent fighting in the capital, between March 12 and April 26, killed at least 1,670 people and forced 400,000 to flee. The battles pitted the government and its Ethiopian allies against clan rivals and Islamic insurgents.

Before Wednesday, one AU soldier had been killed and four injured during the fighting.

Also Wednesday, the aid group CARE International said two of its workers who were kidnapped last week in the semiautonomous Puntland region of Somalia have been released. Puntland has escaped much of the violence that has plagued southern Somalia, but banditry and piracy are a problem in the region.

"The men are unharmed and eager to return to their families," said Beatrice Spadacini, spokeswoman for CARE International's regional office in the Kenyan capital.

On Tuesday, an explosion in southern Somalia killed four people and wounded 20, police said. An unidentified person threw an explosive device into a video hall in Bardheere where people were watching an Indian film, the town's police chief, Mohamed Yare, told The Associated Press.

"Most have serious wounds and we are trying to help, though we do not have enough medicine," said Dr. Bashir Ali of the Shifo Hospital where the injured were taken.

Yare said police did not know who was responsible for the blast or whether it was connected with another blast at a different video hall on Monday. No casualties were reported in that explosion.

Somalia has been mired in chaos since 1991, when warlords overthrew dictator Mohamed Siad Barre and then turned against each other. The transitional government was set up in 2004, but it has failed to assert any real control.