The strike was carried out in the Golis Mountains in northern Somalia, where three IS militants were killed in April.

"At this time, it is assessed the airstrike on May 8 killed thirteen terrorists. Currently, we assess no civilians were injured or killed as a result of this airstrike," said a statement from the US Africa Command, or Africom.

The Islamic State has a relatively small presence in Somalia compared to the Al-Qaeda-linked Shebab.

But IS has been particularly active in the northern Puntland region, establishing training camps and depots for weapons coming mainly from nearby Yemen.

The Shebab, by far the largest radical Islamist group in Somalia, officially integrated into Al-Qaeda in 2012. But a small number of its members -- around 200 -- defected to the IS.

That group, based in semi-autonomous Puntland, is led by Abdulqadir Mumin, who in August 2016 was placed by the US State Department on a list of international terrorists.

IS in Somalia has been the target of previous airstrikes.

Africa Command said an April 14 strike in Somalia killed IS's second in command there, Abdulhakim Dhuqub, who was in charge of the group's attack planning and daily operations.

As of late 2018, Africom put the number of IS fighters in Somalia at between 75 and 250 -- compared to the estimated 3,000 to 7,000 Shebab members.