The strikes were carried out in the area of Jilib in the country's south against the group that "remains a dangerous franchise of Al-Qaeda," the US military said in a statement.

"The initial assessment indicates the strike killed terrorists who were known to play important roles in producing explosives for Al-Shabaab," it said, adding that it appeared so far that no civilians were wounded or killed.

US Major General Dagvin Anderson, special operations commander for Africa, said the strikes also sent a message linked to the withdrawal.

"This strike should demonstrate to any enemy that we stand by our partners and will vigorously defend both ourselves and our partners during this repositioning and future operations," he said in the statement.

The Pentagon announced on December 4 that outgoing President Donald Trump had ordered the removal of most US military and security personnel from Somalia by early 2021.

The US has maintained some 700 troops, personnel and private security contractors in Somalia, conducting both attacks on Al-Shabaab and training Somali forces.

US troops have conducted operations against extremist groups in Somalia since the early 2000s, killing hundreds in mostly conventional aircraft and drone strikes that have caused significant civilian deaths.

Trump's move reflected his drive to disengage US forces from what he calls endless wars abroad, although troops remain deployed across the Middle East and elsewhere.

Al-Shabaab, believed to include between 5,000 and 9,000 fighters, is the main radical Islamist group in the Horn of Africa nation.