Al-Shabab's fighters control much of southern and central Somalia [AFP]

At least two suspected al-Shabab fighters have been wounded after a military air strike hit a convoy near the coast of southern Somalia, witnesses have said.

The overnight strike occurred close to an al-Shabab camp near the port town of Kismayo.

"We heard bangs of explosions first and again after minutes, more loud blasts,'' Ali Abdinur, a resident, told the Associated Press news agency. "I don't know what happened but the place was an al-Shabab camp.''

Hassan Yaqub, an al-Shabab leader, confirmed the attack and said two members of the group were wounded.

"Two enemy aircraft attacked our mujahedeen fighters at a time they were conducting a security patrol near Kismayo,'' Yaqub told a local radio station.

Al-Shabab is the former military wing of the deposed Islamic Courts Union that ruled Somalia before an Ethiopian-led invasion in 2007.

It was not immediately clear who was behind the strike, but US aircraft have attacked al-Shabab fighters in Somalia before.

A US air strike killed a senior leader of the group in 2008, while a US commando raid in 2009 killed an al-Shabab member wanted for the 2002 car bombing of a Kenyan beach resort.

Somalia's fragile, UN-backed government, established in 2004, has been battling al-Shabab who control much of the country's south and centre.

The government controls only a few blocks of Mogadishu and relies on African Union peacekeeping troops to protects key government officials and installations.