Philippine rescuers were scrambling Tuesday to reach dozens of people feared buried under a building near Manila that collapsed a day earlier in a powerful earthquake, as the death toll climbed to 11.

The 6.3 magnitude quake struck northwest of the capital on Monday, scientists from the US Geological Survey said, heavily damaging an airport and sending terrified locals fleeing swaying buildings.

The worst of the damage was in the province of Pampanga, which was the site of all 11 fatalities, disaster officials said. Dozens of others were injured by falling rubble, including in Manila.

The toll could rise as crews travelled across the region to assess damage in isolated villages that lost power and communications in one of the area's strongest tremors in years.

Over 400 aftershocks have been registered since the initial quake, with some as strong as 3.4 magnitude, Philippine seismologists said. Scores of rescuers in the town of Porac were using cranes and jackhammers to peel back the concrete structure of a four-storey building where up to 30 people were unaccounted for.

"They (rescuers) still hear at least one person who is still alive," Pampanga Governor Lilia Pineda told journalists. "This person is buried under concrete slabs."