A hand grenade was thrown late Sunday at a unit of security forces at a major Beirut intersection, police said. The grenade was tossed off a bridge by assailants on a motorbike at the Barbir intersection and fell near a checkpoint for security forces in the Sunni Muslim neighborhood, a major commercial artery in the Lebanese capital. Two civilians who happened to be passing by the area were slightly injured and were treated at a nearby hospital, the police said. At least one vehicle was damaged, according to police, speaking on customary condition of anonymity. The Beirut area has seen three big explosions in the last week, killing a woman and injuring nearly 30 people.