An explosion ripped through fight fans watching a boxing match in the central town of Hilongos late Wednesday, while six people were hurt in a roadside bomb attack on the southern island of Mindanao the same night.
Police said 13 people were also injured in another blast outside a Catholic church during Christmas Eve mass on Mindanao on Saturday.
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"It looks like they are employing diversionary tactics elsewhere to ease military pressure on them," Defence Secretary Delfin Lorenzana told reporters.
Two small Mindanao-based Islamic militant groups, the Bangsamoro Islamic Freedom Fighters (BIFF) and the Maute group, are suspected of involvement in the blasts after they formed a tactical alliance and began sharing bomb-making technology, he added.
The BIFF is a breakaway faction of the Moro Islamic Liberation Front, the country's largest Muslim rebel group, which has been observing a ceasefire with the government.
President Rodrigo Duterte, who began his six-year term in June, has sought to pursue peace negotiations with the front, while ordering a crackdown on Mindanao rebel factions that spurned his peace drive.
Like the Maute group, which has fought skirmishes with government forces in another area of Mindanao this year, the BIFF has been seen using black flags associated with Islamic State group fighters in Iraq and Syria, the military has said.
The third group targeted in the military crackdown is the Abu Sayyaf, blamed for bombings and kidnappings and some of whose leaders have also pledged allegiance to the Islamic state group.
In November Philippine police detained two suspected members of the Maute group who allegedly planted an improvised explosive device inside a rubbish bin near the US embassy in Manila in an attempted bomb attack.
Earlier that month the military blamed the group for a roadside bomb that injured seven of President Rodrigo Duterte's military bodyguards ahead of his visit to the region.
