Soldiers defused two other bombs near the scene of the first blast in the farming town of Kabacan in North Cotabato province, Police Senior Inspector Jarwin Castroberde said.
Four of the victims were brought to a hospital in critical condition, according to Kabacan official David Saure.
Castroberde says investigators were trying to identify the attackers but the suspects include breakaway guerrillas opposed to a peace deal between the Philippine government and the Moro Islamic Liberation Front, the largest insurgent group in the south of the largely Roman Catholic nation.