About 1 600 Ugandan soldiers have been in the city since March as the vanguard of a planned 8 000-strong African Union (AU) forces. No other countries have sent troops yet.

"A team of Burundians arrived in Mogadishu on Monday for a reconnaissance mission," Captain Paddy Ankunda, spokesman for the AU force, told Reuters. "They came to inspect bases for their troops. We expect them (to deploy) as early as September."

Burundi had earlier said its troops would deploy in July.

Without support, the Ugandans have been restricted to guarding Mogadishu's sea and air ports and presidential palace, as well as providing security for top government officials.

The peacekeepers have been the victims of a persistent, Islamist-led insurgency that has targeted government troops and their Ethiopian military allies, mostly with roadside bombs.

Police and residents said at least three civilians were killed in a grenade attack and shooting in the city's sprawling Bakara Market on Tuesday, while a police spokesman said three insurgents were also killed late on Monday in a gun battle.