U.S. President Donald Trump on Saturday said he ordered military airstrikes on a senior Islamic State attack planner and others from the organization in Somalia.

"These killers, who we found hiding in caves, threatened the United States and our Allies," Trump said in a post on Truth Social. "The strikes destroyed the caves they live in, and killed many terrorists without, in any way, harming civilians."

Saturday's strikes were carried out in the Golis Mountains, said Secretary of Defence Pete Hegseth, who added that an initial assessment indicated multiple operatives were killed. He said no civilians were harmed.

Reuters could not independently verify those details.

An official in the Somali president's office, speaking on condition of anonymity, confirmed the strikes and said Somalia's government welcomed the move.

"Somalia cannot be a safe haven for terrorists," said the official, adding that the impact of the strikes was still being assessed.

Hegseth said the strikes degrade Islamic State's ability "to plot and conduct terrorist attacks" threatening the U.S., its partners and innocent civilians.

"[It] sends a clear signal that the United States always stands ready to find and eliminate terrorists who threaten the United States and our allies, even as we conduct robust border-protection and many other operations under President Trump's leadership," he said in a statement.

The United States has periodically carried out airstrikes in Somalia for years, under Republican and Democratic administrations.

A strike, which also targeted Islamic State militants, was carried out by the U.S. in co-ordination with Somalia last year. It killed three members of the group, the U.S. military said.