Philippine authorities were assessing the scale of destruction on Saturday after two powerful offshore earthquakes and more than 800 aftershocks hit Mindanao, killing at least eight people and crippling local infrastructure.

Dazed survivors of a pair of major earthquakes in the southern Philippines awoke on Saturday to scenes of devastation, after hundreds of aftershocks rocked the region overnight.

Many coastal residents of Mindanao island had slept outdoors, fearful of being crushed to death by aftershocks of the 7.4- and 6.7-magnitude quakes that struck off the coast within hours of each other on Friday.

Philippine authorities said at least eight people were killed.

Officials described damage to roads, bridges, schools and other public infrastructure as "minimal" but have yet to determine how many people lost their homes.

In Manay, a Mindanao municipality of 40,000 residents, people were removing debris and sweeping up broken glass from homes and other buildings on Saturday.

"Our small house and our small store were destroyed," resident Ven Lupogan told AFP.

"We have nowhere to sleep. There's no electricity. We have nothing to eat."

The destruction came less than two weeks after a 6.9-magnitude quake struck the central Philippine island of Cebu, killing 75 people and wrecking about 72,000 houses.

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Earthquakes are a near-daily occurrence in the Philippines, which is situated on the Pacific 'Ring of Fire', an arc of intense seismic activity / © AFP

"Most likely housing repair needs," civil defence office deputy administrator Rafaelito Alejandro told AFP when asked about the main long-term needs of quake survivors.

"We're going to give everything that we can provide to the province and municipalities that were affected," Public Works Minister Vince Dizon told reporters during a visit to Manay's heavily damaged government hospital.

Patients lay on beds outside waiting for treatment after having been wheeled out on Friday because government engineers said the building had been structurally compromised.

Dizon said they were considering putting up tent hospitals.

- 800 aftershocks -

Some people in Manay had spent the night in tents, under improvised tarps and hammocks, inside vehicles, and on mats laid out in parks or the sides of streets as aftershocks rippled across the region of 1.8 million people.

Vilma Lagnayo scrambled to save her family's clothes and belongings from their collapsed home in Manay, a town with poor coastal communities that rely on coconut farming and fishing.

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Some people spent the night in tents or improvised shelters after the quakes damaged homes and as aftershocks rippled across the region / © AFP

"Reconstructing (our home) is difficult now... Money is a problem," Lagnayo said.

Nearby shopkeepers cleaned up broken glass and put merchandise back on shelves, AFP journalists saw.

The Philippine seismology office has recorded more than 800 aftershocks since the first quake struck Mindanao, which is riddled by major faults. It said these are expected to last for weeks.

In Mati, about two hours' drive southwest along the coast, Margarita Mulle and her relatives held a wake for her older sister who had earlier died from disease, even as neighbours stayed away after tsunami warnings that have since been lifted.

"In case something happens, they (relatives) will carry the body using a 'tora-tora'," a tearful Mulle said, using a local term for a hand tractor-drawn cart that is a major mode of transport in rural areas of the south.

Earthquakes are a near-daily occurrence in the Philippines, which is situated on the Pacific "Ring of Fire", an arc of intense seismic activity stretching from Japan through Southeast Asia and across the Pacific basin.

An 8.0-magnitude quake off Mindanao island's southwest coast in 1976 unleashed a tsunami that left 8,000 people dead or missing, the Philippines' deadliest natural disaster.