A suicide attacker detonated an explosives-laden vehicle at the Darwish camp," a base used by police units and adjacent to a police academy near the capital's seaport, security official Mohamed Ali said.

He said the blast, which was heard across several Mogadishu neighbourhoods, had caused some casualties but he could not say how many. One witness said two cars were involved in the attack.

"There were two cars that sped up to the camp," said Ahmed Ismail Abdullahi, a local street vendor, who said thick smoke was billowing into the sky as security forces cordoned off the area. He said that gunshots were heard in the area just before the attack, at a time when security forces generally line up to report for duty.

There was no immediate claim of responsibility for the attack, which took place shortly after 8:30 am (0530 GMT) but recent such operations in Mogadishu have all been conducted by the al Qaeda linked Shebab insurgent group.