Casualties were reported after Somalia's al-Shabab terrorists attacked a military base of the African Union Transition Mission in Somalia on Tuesday.

The attack started early Tuesday when a vehicle rammed into the fence surrounding the base and exploded in El-Baraf, a strategic town 150 kilometers (93 miles) northeast of the capital Mogadishu in the Middle Shabelle region, residents said.

Residents said they heard massive explosions at the base followed by gunfire.

"While we were preparing to perform the dawn prayer, we heard two loud explosions that hit the base ... followed by a heavy exchange of gunfire between the militants and Burundi troops that lasted for almost an hour," Abshir Ali, a resident of El-Baraf said by phone.

Somalia's state media confirmed the attack and said the Burundi soldiers at the base repulsed it. Officials have not given an estimate of the numbers killed in the battle.

Plumes of smoke rose from the camp during the fierce gun battle that forced some residents to flee the town, said residents. Helicopters from the African Union force were used to help the Burundi soldiers maintain control of the camp, they said.

AU forces dispatched helicopter gunships after the pre-dawn car bomb and gun attack on a camp housing Burundian peacekeepers near Ceel Baraf, a village some 160 kilometers (100 miles) northeast of the capital Mogadishu, the sources said.

A high-ranking Burundian military officer told AFP that about 30 soldiers were killed and another 22 wounded, while a dozen were missing. There was no confirmation about the toll from Somali or AU officials.

"There was heavy fighting and casualties inflicted on both sides, but we don't have more details about this incident so far," local military commander Mohamed Ali told AFP by phone.

"They launched the attack with a car bomb blast before a heavy exchange of gunfire broke out," he added.

Al-Shabab, which has been waging a deadly insurgency against Somalia's fragile central government for more than a decade, claimed responsibility for the assault.

It was the first such major attack on a peacekeeping base since the AU Transition Mission in Somalia ATMIS) replaced the previous AMISOM peacekeeping force on April 1.

There has been no comment from ATMIS or the central government on the attack, which comes with the country locked in a deep political crisis over delayed elections and facing the threat of famine.