* Al Shabaab claims blast

* Mayoral spokesman said 5 people also wounded (updates death toll, adds details, byline)

By Feisal Omar and Abdirahman Hussein

MOGADISHU, April 11 (Reuters) - A car bomb at local government headquarters in Mogadishu killed five people and wounded five, an official said, in an attack claimed by Somali Islamist group al Shabaab.

Al Shabaab has frequently attacked government targets, hotels and restaurants in the capital since being pushed out by African Union peacekeeping forces in 2011 and rebasing in the country's south.

"We are behind the governor HQ attack," Abdiasis Abu Musab, the group's military operations spokesman, said.

On Saturday, another bomb killed three and wounded five in Mogadishu.

A police spokesman said that in Monday's attack a suicide bomber rammed a car packed with explosives into the entrance of the headquarters.

But mayoral spokesman Abdifatah Omar blamed a car parked at the rear of the heavily fortified compound.

"So far we have confirmed five civilians died and five others were injured," he said.

The blast, which other reports suggested may have been detonated remotely, destroyed part of a guardroom.

"We heard a huge bang and then (saw) huge clouds of smoke over us. We are safe," one female worker inside the compound, who identified herself as Nasra, told Reuters. (Additional reporting by Abdi Sheikh and Ismail Taxta; Writing by Wendell Roelf, editing by John Stonestreet)