NAIROBI: Kenyan police officers were among those killed when gunmen suspected to be from Islamist militant group al Shabaab attacked a bus on Friday near the border with Somalia, President Uhuru Kenyatta's office said on Saturday.

The vehicle belonging to the Medina Bus Company was attacked on a lonely stretch of road in the Kotulo area as it travelled between the towns of Wajir and Mandera.

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

Police said 10 people had been killed and that the attackers had specifically targeted non-Somalis after flagging down the bus. The area is mostly inhabited by ethnic Somali Kenyans.

"The attackers separated local Somalis from non-locals, and in the process, shot 10 non-locals dead," police spokesman Charles Owino said in a statement.

He said security forces were pursuing the gunmen and that the driver and conductor of the bus were in custody and helping with investigations.

Al Shabaab said it had carried out the attack and that it had killed 10 people including "secret security agents and government employees".

The Somali-based group has targeted Kenya many times since the East African nation sent troops across the border to fight the militants in their homeland in October 2011.