Heavily armed fighters from the al-Shabab extremist group attacked a base for African Union peacekeepers in southwestern Somalia on Friday, blasting their way into the compound and exchanging fire with peacekeepers, a Somali military official said.

Dozens of al-Shabab fighters started a complex attack on the military base which is run by Kenyan troops who are part of the African Union force in the town of El-Ade, not far from the Kenyan border, Ahmed Hassan told The Associated Press by phone from Elwak, a town near the scene of the latest attack.

The attack started with a suicide car bomb, and then heavy gunfire was heard as militants stormed into the base, he said.

Fighting is still going on inside the base, he said. Initial reports have claimed that dozens have been killed during the attack.

Al-Shabab reported on its online radio that its fighters had managed to penetrate the base and were fighting African Union troops.

Despite being pushed out of Somalia's major cities and towns, al-Shabab continues to launch deadly guerrilla attacks across the Horn of Africa country.

The group, which has ties with al-Qaida, has also carried out many deadly attacks inside Kenya.