In the first incident, two bombs exploded late Wednesday in the central island of Leyte, wounding 27 people who were watching a boxing match in Hilongos, police said.
Another unexploded bomb was also found in the town, which is about 620 kilometres (385 miles) south of Manila, said the town's mayor Albert Villahermosa.
A bomb went off on a highway on the southern island of Mindanao barely an hour later, wounding six people, the military said.
"A lamppost was catapulted from the impact of the explosion," said Lieutenant Colonel Edgar Delos Reyes.
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Police said it was too early to say if the Wednesday bombings were connected or what the perpetrators' motives might be.
Mindanao has been wracked by bombings and other forms of violence carried out by Muslim extremists who consider the region as their ancestral homeland, leading to separatist conflicts with the majority-Christian government.
Muslim extremists have also been blamed for bombings outside Mindanao, such as the discovery of a bomb near the US embassy in Manila in November.