In the worst fighting this year in the war-scarred coastal city, at Shabaab rebels have been battling Somali police and soldiers in mortar and machine-gun exchanges that have sent tens of thousands of residents fleeing Mogadishu.

The battle to control the city is the biggest test to date for the new government of President Sheikh Sharif Ahmed-himself a moderate Islamist-which was formed in January under a UN-brokered reconciliation process in neighbouring Djibouti.

The violence has drawn in several hundred foreign jihadists, experts say, as well as fuelling a humanitarian crisis, allowing piracy to flourish offshore, and perpetuating a cycle of civil conflict since the 1991 fall of a Somali governor.

In a favoured tactic of the rebels, a roadside bomb on June 1 killed at least 10 people, including four officers, police said.

The local Elman Peace and Human Rights Organisation said that brought to at least 38 the number killed in the last 48 hours in Mogadishu. About 70 have died in the last two weeks.