OUAGADOUGOU (Reuters) - Unidentified armed men killed five police officers in an attack on a police station in northern Burkina Faso in the early hours of Sunday, a government source and three security sources said.

       The incident occurred in Sourou province in the borderlands near Mali, where Islamist groups with links to al Qaeda and Islamic State have increased attacks in recent years despite international efforts to stamp them out.

       The attackers struck between 5 a.m. and 6 a.m. and stole one vehicle and eight motorcycles, the government source said.

       Islamist attacks have surged across Africa's Sahel region, killing thousands and driving millions from their homes in Burkina Faso, Mali and Niger. About 1.2 million people have been displaced by the violence in Burkina Faso alone.

       (Reporting by Thiam Ndiaga; Writing by Alessandra Prentice; Editing by Alison Williams)