The United States military says it has killed 35 fighters from the al-Shabab extremist group with an airstrike in central Somalia, not far from the Ethiopian border.

In a statement on Monday, the US military command for the African continent said the airstrike took place on Sunday about 37km east of Beledweyne in the Hiran region and targeted the fighters as they were travelling in a rural area.

The US has dramatically increased airstrikes against the al-Qaeda-linked al-Shabab, the deadliest extremist group in Africa, since President Donald Trump took office.

Authorities and experts acknowledge that it will take more than airstrikes to defeat the extremist group, which continues to hold large parts of rural central and southern Somalia and carry out deadly attacks in the capital, Mogadishu.