At least seven people were killed onthe New Year's Eve in a blast in the southern Philippine province of Sultan Kudarat.
More than 30 others were injured when someone lobbed a grenade into a row of stalls selling firecrackers, setting off a series of explosions, the ABS-CBN news channel reported on Wednesday.
So far no one has claimed responsibility for the incident and a manhunt has been launched for the perpetrator, the military said.
The number of fatalities may still increase because many of the injured are in serious condition.