At least 39 people have been injured in two separate bomb attacks in the Philippines, authorities said Thursday.

In the first incident, two bombs exploded late Wednesday in the central island of Leyte, wounding 33 people who were watching a boxing match in Hilongos, government officials 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.

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39 people have been injured in the two separate bomb attacks in the Philippines. Source: AAP

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.

The blast in Aleosan, hundreds of kilometres south of Hilongos, was close to the site of a Christmas Eve church bombing that injured 13.

Police said it was too early to say if Wednesday's bombings were connected or what the perpetrators' motives might be.

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Filipino President Rodrigo Duterte visiting an explosion victim in the town of Midsayap, North Cotabato province, Philippines. Source: AAP

Mindanao has been wracked by bombings and other forms of violence carried out by Muslim extremists who consider the region their ancestral homeland, waging a decades-long independence struggle that is believed to have claimed more than 120,000 lives.

Muslim extremists have also been blamed for attacks outside Mindanao, such as the discovery of a bomb near the US embassy in Manila in November.

In the deadliest such attack recently, 15 people were killed in an explosion in President Rodrigo Duterte's hometown of Davao in Mindanao in September.