Al-Qaeda-linked Shebab commandos on Thursday attacked an African Union military base in central Somalia dressed in stolen government army uniforms, killing at least two soldiers from Djibouti, the AU force said.

The Shebab said their gunmen stormed the compound of a hotel where Djiboutian troops with the AU force were based in the town of Bulla Burde, some 200 kilometres (125 miles) north of the capital Mogadishu, their spokesman Abdulaziz Abu Musab told AFP.

"The area command headquarters (of the AU force) was attacked, these attacks will continue," Musab said, boasting to have killed six AU troops.

However, Elio Yao, spokesman for the UN-backed AU mission in Somalia (AMISOM), rejected the claims, saying the gunmen failed to enter the compound but had killed two Djiboutians in a firefight.

The two Shebab fighters "dressed in military fatigues or uniform" were also killed, Yao said.

The attack is the latest by the Shebab, in retaliation for the AU offensive to root them out of areas of the war-torn country still under their control.

Residents reported a heavy blast followed by fierce gunfire and explosions for about hour, beginning around dawn on Thursday.

"There was a loud explosion before a firefight broke out," said Ahmed Abdirisak, a local resident.

"There was heavy exchange of gunfire, it continued about an hour.. there are several dead bodies strewn around," said resident Hassan Mohamed.

The town was seized from the Shebab in March.

After withdrawing from fixed positions in the capital Mogadishu nearly three years ago, the Shebab have lost most large towns to the AU and government soldiers. However, they still regularly launch guerrilla raids.

Recent Shebab attacks in Somalia have targeted key areas of government, or the security forces, in an apparent bid to discredit claims by the authorities and AU troops that they are winning the war.