Two people were killed when a grenade they were carrying in Pradera, a town in the southwestern Colombian province of Valle del Cauca, exploded, media reports said.
Between three and 17 people were wounded by the blast, which occurred Wednesday near the town's main plaza, where a Halloween celebration was being held.
"A girl sustained serious leg injuries" and the families that had gathered in the plaza "left in an orderly fashion," Pradera Mayor Adolfo Escobar told the El Tiempo newspaper.
Initial reports are that the individuals killed in the blast had planned to attack the police station, the mayor said.
The two people killed in the explosion have not been identified and police have not said why they were carrying the grenade.
The Revolutionary Armed Forces of Colombia, or FARC, guerrilla group has staged attacks in recent months on security forces patrols and police stations in the area. EFE