An African Union Mission in Somalia (AMISOM) military base has been attacked in a dawn raid that has been claimed by armed group al-Shabab.

A tweet from AMISOM confirmed the raid started on Friday at its outpost in Lego, about 100km northwest of the Somali capital Mogadishu.

The mission is manned by Burundian soldiers who are part of Somalia's 22,000 strong mission.

A local official told the Associated Press news agency that fighters attacked the base entrance with a suicide car bomb at the start of the assault.

Witnesses said the fighters used machine guns and rocket-propelled grenades.

"They managed to infiltrate the entrance after the blast. It was a complex attack," said Mohammed Haji, an official in the Lower Shabelle region, saying that many people were believed to have died in the attack.

There was no immediate confirmation of casualties, but an al- Shabab spokesman claimed the group had taken control of the base, killing "dozens", and had raised its flag and seized weapons.

"The black Islamic flag is flying over the main base of AMISOM in Lego this morning and the dead bodies of the enemy are scattered around the area, the mujahideen fighters have taken all their military supplies," Mohamed Abu-Yahya, an al-Shabab commander, told the AFP news agency.

Hassan Mohamed, a resident, confirmed the heavy fighting, saying: "We could see smoke and hear explosions."

Al-Shabab had earlier vowed it would step up attacks during the month of Ramadan.

Source: Agencies