Two grenades were recovered by police, one of which did not explode in the incident late Sunday, said Romeo Galgo, a spokesman for the Central Mindanao regional police.
One of the injured was in serious condition, Galgo said.
Witnesses said two men on a motorcycle tossed the grenades at the carnival in Esparanza town.
Bloodied slippers, shirts, shoes and other items littered the blast site, and police investigators were still searching for possible evidence.
- DPA