By Abdi Sheikh and Abdirahman Hussein
MOGADISHU, Aug 31 (Reuters) - Islamist rebels blew up a car bomb on Sunday at a national-intelligence site in Somalia's capital where suspected militants are held, and gunmen then attacked the site, officials and the rebel group said.
Seven militants were killed in the attack and in fighting at the Mogadishu facility, according to an intelligence officer, who asked that he be identified only as Nur. He gave no details on casualties among the security forces, if any.
Ahmed Hussein, a senior police officer, confirmed the car bombing and armed attack and added that the facility included underground cells.
"It seems their target was to cause a mess here and thus free their militant colleagues held in the underground cells, but that will not happen," Nur said.
The Islamist group al Shabaab claimed responsibility for the assault, in a statement by Sheikh Abdiasis Abu Musab, al Shabaab's spokesman for military operations, to Reuters. It was the latest in a series of attacks in Mogadishu in recent months, including a July raid on the presidential compound.
That compound is near the national intelligence site, and it was also attacked using what has become a familiar tactic: a vehicle tries to blast its way through perimeter security and gunmen charge in afterwards.
The president was not present during the July raid.
Al Shabaab, which wants to impose its own strict version of Islam, controlled Mogadishu and the southern region of Somalia from 2006 to 2011. It was driven out of the capital by peacekeeping forces deployed by the African Union.
African forces launched a new offensive this year to drive the Islamists out of towns and other areas they still control. Several centres have been retaken, but al Shabaab remains in control of some towns and swathes of countryside. (Writing by Edmund Blair in Nairobi; Editing by Larry King)