Lebanese security forces set up checkpoints and patrols in the northern city of Tripoli, raided homes and arrested more than 20 people in a push to control sectarian violence fuelled by the war in Syria.

At least 27 people have been killed over the past three weeks in Tripoli in clashes between Sunni Muslims and members of the Alawite sect, an off-shoot of Shi’ite Islam.

The long-standing rivalry between the two sides has been worsened by the violence in Syria, which is sunk in a three-year-old conflict that has killed over 150,000 people and become increasingly sectarian.