(UPDATED) The Philippine Institute of Volcanology and Seismology (Phivolcs) raised a tsunami warning in the coastal areas of Surigao del Sur, and Davao Oriental Saturday night after a magnitude 6.9 earthquake struck eastern Mindanao.

Phivolcs urged residents in coastal areas of the two provinces to immediately evacuate to higher ground or move farther inland amid the threat of a tsunami.

"Based on the local tsunami scenario database, it is expected to experience wave heights of more than one meter above the normal tides and may be higher on enclosed bays and straits. Destructive tsunami is expected with life threatening wave heights," Phivolcs warned.

The US Tsunami Warning Center, in an advisory following the quake, warned possible tsunami waves of 1-3 meters above the tidal height in eastern Mindanao.

Phivolcs said the first tsunami waves will arrive between 10:37 p.m. to 11:59 p.m Saturday and the waves may continue for hours.

"Owners of boats in harbors, estuaries or shallow coastal water of the above-mentioned provinces should secure their boats and move away from the waterfront. Boats already at sea during this period should stay offshore in deep waters until further advised," Phivolcs added.

According to Phivolcs, the undersea earthquake, which was tectonic in origin, occurred at 10:37 p.m. some 42 kilometers northeast of Hinatuan town at a depth of 8 kilometers.

• M6.9 quake strikes off Surigao del Sur

Intensity 5 was recorded in Bislig, Surigao del Sur and Cabadbaran, Agusan del Norte.

The quake is expected to trigger aftershocks.

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