The explosion of a fragmentation grenade has left 12 people injured in the troubled, hillside eastern Medellin neighborhood of La Sierra, Caracol Radio reported Thursday.
Three policemen and nine civilians were wounded, inluding a young child, who were all treated for their varying degrees of injury.
Most patients have since been discharged from the various medical centers to which they were sent, although one policeman remains hospitalized.
The incident has put the police authorities on alert in the area after there were clashes Sunday between rival gangs, as well as the police, that left one dead and four injured.
Authorities offered an $11,000 reward for information leading to the capture of those responsible for the grenade attack.