A Lebanese policeman was killed Friday by unk**wn gunmen in the **rthern city of Tripoli, which has been rocked by violence linked to the Syrian conflict, a security source said. "Two armed men on a motorbike opened fire with automatic ******* on a Range Rover carrying Butrus al-Bayya, a member of the Internal Security Service," a security source told AFP. It remains unclear if the murders are linked to chronic violence in Tripoli, where decades-long tensions has been exacerbated by the conflict in neighbouring Syria.