The clashes shattered a week-long lull in the seaside capital, a theatre of fighting since Ethiopia-backed government forces routed an Islamist movement in January, ending its six-month rule.

The rebels attacked after well-armed Ethiopian forces pulled out of southern Mogadishu's Wardhigley camp, where they have been based for nearly a year, prompting hours-long clashes.

"They exchanged machine gun fire, anti-aircraft weapons and rocket-propelled grenades. Stray bullets wounded two civilians," said resident Ayan Mohamed. Several other witnesses confirmed the artillery duels.

It was not immediately clear whether the clashes left fatalities.

Pro-Islamist militants, chanting Allahu Akbur (God is Great) seized control of central Somalia town of Bulo-Burde, about 230 kilometres (145 miles) north of the capital, freeing prisoners in the township as government forces fled, witnesses said.

"Heavily-armed pro-Islamists entered the town this morning and took control after a exchange of gunfire with government forces," said a Bulo Burde authority official, who requested to remain unnamed.

"The militia forced people to flee the town and also plundered offices of the local authorities," said Osmail Mumin Adan, a resident of the township, adding that fatalities could not be confirmed since people had left.

Islamist militants have staged a deadly insurgency since they were ousted in January, paralysing the government's bid to restore law and order in the city, where at least 600,000 have been displaced.

Violence and state bureaucracy have choked delivery of humanitarian supplies to a million people across the country, setting the stage for Africa's worst humanitarian crisis, according to the United Nations.

Bloody clan brawls and power struggles that erupted after the 1991 ouster of dictator Mohamed Siad Barre have defied numerous bids to restore stability in the Horn of Africa nation.

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