US war planes carried out a strike in southern Somalia on Monday targeting a senior leader of the Shebab militia, the Pentagon said, without giving any details of casualties.

Military spokesman Rear Adm. John Kirby said the raid hit a target in Saakow, shortly after the Islamist rebel group's intelligence chief surrendered to government and African Union forces.

Kirby did not identify the targeted militant chief by name.

"At this time, we do not assess there to be any civilian or bystander casualties," he said.

"We are assessing the results of the operation and will provide additional information, when appropriate, as details become available."

If a senior militant was killed in the strike, it would be the latest in a series of setbacks for the militia since the death of its former leader Ahmed Abdi Godane in another US attack in September.

On Saturday, officials said the al-Qaida-affiliated group's intelligence chief Zakariya Ismail Ahmed Hersi, the subject of a $3 million US bounty, had surrendered to Somali government forces.

But despite recent setbacks, the Shebab, which is fighting to topple a weak but internationally recognized government propped up by African Union troops, has proved resilient.

On Thursday, its fighters launched a brazen attack on the AU force's heavily-fortified headquarters at Mogadishu's airport, killing three soldiers and a civilian contractor.

The AU force, deployed since 2007, counts some 22,000 troops and has pushed the Shebab out of the capital, but the Islamists still hold large swathes of territory in the south and center of the country.

Recent rebel attacks have targeted key government and security sites in an apparent bid to discredit claims by the authorities and the African Union that they are winning the war.

The United States has no permanently deployed ground force in Somalia but supports the government and sometimes deploys air power or special forces against targets linked to al-Qaida.