(Adds identity of al Shabaab explosives expert)
MOGADISHU, Oct 28 (Reuters) - A suspected U.S. drone strike killed at least two Islamist al Shabaab insurgents driving in a car south of the Somali capital Mogadishu, residents said on Monday.
Ibrahim Ali, believed to be al Shabaab's lead explosives expert, was among the dead, one U.S. official said, speaking to Reuters on condition of anonymity, without offering details on how the United States carried out the strike.
Al Shabaab claimed responsibility for a September attack on the Westgate shopping mall in Nairobi that killed at least 67 people.
Witnesses to Monday's strike said the drone fired a missile at the car in the outskirts of Jilib town in the Middle Jubba region, some 75 miles (120 km) north of the port of Kismayu in the country's South.
"This afternoon, I heard a big crash and saw a drone disappearing far into the sky, at least two militants died," said Hassan Nur, a resident in the area.
"I witnessed a Suzuki car burning, many al Shabaab men came to the scene. I could see them carry the remains of two corpses. It was a heavy missile that the drone dropped. Many cars were driving ahead of me but the drone targeted this Suzuki," he added.
Other residents at the scene also said they had seen the strike. Somalia officials and police were not immediately able to comment, largely because the rebels control a vast area around where the drone struck.
Al Shabaab officials declined to comment.
Al Shabaab was driven out of Mogadishu in late 2011 and are struggling to hold on to territory elsewhere in the face of attacks by Kenyan, Ethiopian and African Union forces trying to prevent Islamist militancy spreading out from Somalia.
Still, Western nations are worried that Somalia will sink back into chaos and provide a launchpad for Islamist militancy despite a fragile recovery after two decades of war.
Al Shabaab, which is affiliated with al Qaeda, said in January 2011 that a missile launched from a drone had killed Bilal el Berjawi, a Lebanese al Shabaab fighter who held a British passport.
Another missile killed four foreign militants south of the Somali capital Mogadishu in February 2012.
(Reporting by Feisal Omar; additional reporting by Phil Stewart in Washington; Writing by James Macharia; editing by Ralph Boulton and Cynthia Osterman)