The Phivolcs agency warned of damage and aftershocks from the strong offshore quake, which struck in waters off Manay town in Davao Oriental in the Mindanao region.
It said Friday morning's quake happened at a depth of 10 kilometres. The agency called on people in coastal towns in the central and southern Philippines to immediately evacuate to higher ground or move further inland, saying wave heights up to more than one metre above normal tides could be expected.
Philippine President Ferdinand Marcos Jr said authorities are assessing the situation on the ground, and search and rescue efforts are being prepared and will be deployed as soon as it is safe to do so.
"We are working round the clock to ensure that help reaches everyone who needs it," Marcos said in a statement.
Office of Civil Defence deputy administrator Bernardo Rafaelito Alejandro IV warned that tsunami waves could hit six nearby coastal provinces from Davao Oriental up to two hours after the earthquake struck at 9.43am local time.
"We urge these coastal communities to be on alert and immediately evacuate to higher grounds until further notice," Alejandro said in a video news briefing.
"Owners of boats in harbours and those in the coastal areas ... should secure their boats and move away from the waterfronts."
A tsunami warning was also issued in Indonesia for its northern Sulawesi and Papua regions, warning of waves as high as 50cm hitting those shorelines.
Indonesia's Meteorology, Climatology, and Geophysics Agency said in a statement that residents in the area should be aware and stay away from beaches and riverbanks.
The US Tsunami Warning System issued a tsunami threat, saying hazardous tsunami waves are possible for coasts located within 300km of the earthquake's epicentre.
The Pacific Tsunami Warning Centre said waves of one to three metres above tide level were possible in the Philippines, and said some coasts in Indonesia and Palau could see waves of up to one metre.
The governor of the southern Philippine province of Davao Oriental said people panicked when the earthquake struck.
"Some buildings were reported to have been damaged," Edwin Jubahib told broadcaster DZMM. "It was very strong."
Local authorities in the affected region in the Philippines could not immediately be reached.
The strong quake came two weeks after the Philippines experienced its deadliest quake in more than a decade, with 72 people killed on the island of Cebu. That was a magnitude of 6.9 and also struck offshore.
The Philippines sits on the Pacific "Ring of Fire" and experiences more than 800 quakes each year.
With AP
