The quake hit about 20 kilometres (12 miles away) from Manay in the Mindanao region at 9:43 am (0143 GMT), the United States Geological Survey (USGS) said.
"Destructive tsunami is expected with life-threatening wave heights" on the archipelago nation's east coast, the Philippine Institute of Volcanology and Seismology reported.
Coastal residents in these areas "are strongly advised to immediately evacuate to higher grounds or move farther inland," it added.
Waves of up to three metres were forecast for threatened areas in the Philippines and up to a metre-high waves in Palau and Indonesia, the US National Oceanic and Atmospheric Administration said.
There were no immediate reports of casualties, though police officer Dianne Lacorda told AFP the province of Davao Oriental, which includes Manay, expects damage.
"Our tumblers on the table were moving and falling," she said, adding power and communication lines have been cut and the authorities are currently unable to assess the potential damage in some areas.
- 'Shaking was so strong' -
Christine Sierte, a teacher in the town of Compostela near Manay, told AFP she was in the middle of an online meeting when the violent shaking started.
"It was very slow at first then it got stronger.... That's the longest time of my life. We weren't able to walk out of the building immediately because the shaking was so strong," she said.
"The ceilings of some offices fell, but luckily no one was injured," she said, though some of the school's 1,000-odd students "suffered panic attacks and difficulty in breathing".
Kath Cortez, a local journalist based in Davao city to the west of Manay, told AFP the ground floor walls of her family's house were showing small cracks.
"I was surprised by the strength. I had just woken up and was about to take a shower," she said, adding members of her family ran out of the house.
Around the same time as the Philippine quake, USGS reported a shallow 6.2 magnitude temblor just over 140 kilometres southeast of Manus Island in Papua New Guinea.
A 99-kilometre-deep quake struck on Tuesday near the Pacific island nation's second-largest city of Lae. No major damage was reported
The latest Philippine quake struck just 11 days after a 6.9-magnitude quake killed 74 people and destroyed or damaged about 72,000 houses in the central island of Cebu.
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.
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