Police in Colombia say at least seven people were killed and 20 injured by a grenade attack in the town of Cajibio late Saturday.

The police say unidentified assailants threw the grenade during a celebration being held at a local school. The motive has not been determined.

Both left-wing and right-wing military groups are active in the region, located in Cauca province southwest of Bogota.

Some information for this report provided by AFP and Reuters.