A Kenyan official says suspected members of the Somalia-based extremist group al-Shabab have killed five police officers in the northern county of Mandera.

North Eastern regional coordinator Mohamud Saleh said Wednesday the vehicle carrying the three police reservists and two administration police officers was attacked.

He says several other officers were injured in a second attack on security officials who responded Tuesday evening along the Elwak-Kotulo road.

Al-Shabab has carried out a series of attacks in Kenya since 2011, when Kenya deployed troops to neighboring Somalia to fight the extremists.

Al-Shabab has vowed retribution for the Kenyan troop presence in Somalia. In recent years, most of the al-Shabab attacks have been limited to areas near the Somali border and have mainly targeted security forces.