MANILA (4th UPDATE) — A magnitude 7.4 earthquake — updated from magnitude 6.9 — struck off Surigao del Sur on Saturday night, spawning strong aftershocks and triggering a tsunami warning, the Philippine Institute of Volcanology and Seismology (Phivolcs) said.

The powerful quake that also shook surrounding provinces sent people near coastal areas to move to higher ground or further inland due to the tsunami warning that was eventually lifted Sunday morning.

• Major aftershocks jolt Mindanao after magnitude 7.4 quake

Phivolcs said the highest waves produced by the tremor were .64 meters (25 inches) tall on Mawes Island, Hinatuan town, which was near the epicenter.

"Destructive" Intensity 7 was felt in Tandag City, while "very strong" Intensity 6 was reported in Hinatuan, Bayabas, and Bislig City in Surigao del Sur.

Neighboring Maco and Monkayo towns in Davao de Oro also felt Intensity 6, according to Phivolcs' third bulletin on the magnitude 7.4 quake, which was generated by the Philippine trench.

The potentially damaging tremor — one of the strongest in recent years — also saw people fleeing buildings and evacuating a hospital, with panicked revelers at a bar in Davao City running and ducking for cover as they felt a strong Intensity 5 shaking.

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• Strong quake damages houses in Agusan del Sur
• Panic, prayers after magnitude 6.9 quake strikes eastern Mindanao

MINDANAO AIRPORTS

The Civil Aviation Authority of the Philippines on Sunday reported minor damage seen at some Mindanao airports after a magnitude 7.4 earthquake.

Davao International Airport did not suffer significant damage, except for a few fallen wall tiles near the international arrival elevator, according to the CAAP.

It said passengers and personnel at the airports are safe and that the Airports Quick Response Team is currently inspecting runways and passenger terminal buildings.

Despite the minor damage, all flights in Mindanao airports are operating normally, the CAAP noted.

• Panic, prayers after magnitude 6.9 quake strikes eastern Mindanao

AFTERSHOCKS TO PERSIST

The undersea tectonic tremor — initially measured at magnitude 6.9 — occurred at 10:37 p.m. some 29 kilometers northeast of Hinatuan at a shallow depth of 26 kilometers.

In its latest update, Phivolcs said at least 765 aftershocks of up to magnitude 6.2 had been recorded following the major quake. Of the number, 7 aftershocks were felt.

Phivolcs director Teresito Bacolcol told journalists at a press briefing that aftershocks could still be expected for days to a few weeks. He however noted that the aftershocks would decrease in magnitude.

• Strong quake damages houses in Agusan del Sur

NO CASUALTIES SO FAR

Hinatuan police Sergeant Joseph Lambo said the quake was "very strong" but that there were no reports of casualties or major property damage.

"Appliances fell off the shelves at the police office and two TV sets were broken. The motorcycles parked outside also tumbled down," Lambo told AFP news agency.

"Right now we don't have reports of damage or casualties but people are evacuating because of the tsunami alert."

Lambo said the 45,000 residents in the municipality had been ordered to leave their homes and many were going on foot or in vehicles to higher ground.

The National Disaster Risk Reduction and Management Council said it is coordinating with local disaster officials following the powerful quake.

The temblor came nearly two weeks after a 6.7 magnitude quake hit Mindanao, killing at least nine people, shaking buildings, and causing part of the ceiling of a shopping mall to collapse.

Quakes are a daily occurrence in the Philippines, which sits along the Pacific "Ring of Fire," an arc of intense seismic and volcanic activity that stretches from Japan through Southeast Asia and across the Pacific basin.

Most are too weak to be felt by humans, but strong and destructive quakes come at random with no technology available to predict when and where they will happen.

—with reports from Jacque Manabat, Anjo Bagaoisan, Rowegie Abanto, ABS-CBN News, and Agence France-Presse