Somalia's former defence minister was killed in a car bomb on Monday, the latest in a string of attacks in the capital Mogadishu, police said.

There was no immediate claim of responsibility for the explosion in the central K4 district of the city, but Al-Qaeda-linked Shebab insurgents have carried out similar bombings in the past.

Muhidin Mohamed, who was defence minister in 2008, "died after the violent elements attached an explosive device beneath the driver's seat of his car," said police officer Ibrahim Mohamed. "Another person was wounded in the attack."

The Shebab is fighting to overthrow the internationally-backed government in Mogadishu, which is protected by 22,000 African Union troops.

"I heard the explosion near the K4 area and I saw a dead body - he was horribly wounded with blood all over his body," said Samiro Muktar, a witness.

Meanwhile a military drone reportedly crashed in southern Somalia on Monday in a remote area held by Shebab fighters, residents said.

"We saw what looked like a small aircraft crashing in the mountains," said Abudlahi Muhidin, a resident in a nearby village. "Shebab fighters carried away the wreckage on a vehicle."

Several Shebab commanders have been reportedly killed by US drone strikes.

Shebab insurgents said they had seized the wreckage of an unmanned aircraft, which landed in a hilly region south of Bardhere in the far southern Gedo district, close to the border of Kenya and Ethiopia.

"Mujahedeen fighters secured control of the wreckage of the plane and the equipment it carried," a pro-Shebab website claimed.

The Islamists are on a mission to disprove claims they are close to defeat since being routed from Mogadishu in mid-2011.

Last week the Shebab claimed responsibility for a bomb attack which ripped a hole in a passenger plane shortly after takeoff from the capital Mogadishu earlier this month.