Seven police officers among dead after gunmen attacked a bus in northeast Kenya

At least ten people, including several police officers, have been killed when shooters attacked a bus in northeast Kenya.

On a lonely stretch of road, the vehicle belonging to the Medina Bus Company was attacked on Friday in the Kotulo area as it travelled between the towns of Wajir and Mandera, close to the border with Somalia.

"People, among them police officers, were brutally murdered," President Uhuru Kenyatta's office said in a statement on Saturday.

The Somalia-based al-Shabab armed group, which has also carried out several attacks in neighbouring Kenya, took responsibility for the assault, saying it had killed people that included "secret security agents and government employees".

Police said ten people had been killed and that the attackers had explicitly targeted non-Somalis after flagging down the bus. Ethnic Somali Kenyans mostly inhabit the area.

Seven police officers were killed in the attack, local media reported.

"The attackers had shot all the victims outside the bus at close range, but police and the government did not comment on those accounts," said witness.

Al-Shabab has been fighting for more than ten years to overthrow successive internationally-backed Somali governments and has previously attacked many vehicles.

Although Somalia is slowly rebuilding after years of devastating conflict, it suffers regular bombings and assaults claimed by the group.