Sunday's strike took place in the Hiran region of central Somalia and targeted armed Shabaab fighters "as they were transitioning between locations in a rural area" and trying to "mass their forces," the US military's Africa Command said in a statement.

"At this time, it is assessed this air strike killed 35 terrorists," the statement read.

Although the military did not specify, such air strikes in Somalia are typically carried out by armed drones.

The Pentagon has increased the rate of strikes in Somalia in recent years, partly because President Donald Trump loosened constraints on when the US military can take action against alleged terrorists.

Shabaab fighters were pushed out of Somalia's capital in 2011, and subsequently from other towns and cities, by African Union troops.

But the Islamists still hold sway in large parts of the countryside.

They launch regular gun and bomb attacks on government, military and civilian targets in Mogadishu as well as ambushes on military convoys and outposts.

In one strike last month, Africa Command said it killed 52 Somali militants.

In December, the US military said it had killed 62 Shabaab militants during six air strikes in the Horn of Africa nation.

But Africa Command head General Thomas Waldhauser this month told US lawmakers that air strikes alone would not stop Shabaab, and he called on Somalia's army to take more responsibility in the fight.