Philippines earthquake: 6.3-magnitude tremor shakes Luzon

UPDATE: Eleven dead as rescuers search for survivors

A powerful, 6.3-magnitude earthquake struck the northern Philippines on Monday, sending thousands of people fleeing high-rises in Manila as the buildings shook.

At least five people were killed when two buildings collapsed near the epicentre, which was in Gutad, Pampanga, about 100 kilometres north of Manila.

The US Geological Survey said the earthquake struck at a depth of 40km.

Three bodies have been pulled out of a collapsed building in the town of Porac in Pampanga, while an old woman and her grandchild were crushed to death by a building in the town of Lubao, provincial governor Lilia Pineda told ABS-CBN television.

Twenty-nine people were being treated for injuries in Porac.

"The quake has caused a blackout," Ms Pineda said. She said the power cuts were hampering rescue efforts as night closed in.

At nearby Clark Airport, which is a destination for Emirates airline, witnesses shared photos of a damaged terminal building. Cebu Pacific, a local carrier, has cancelled flights.

Manila office workers raced into the streets as emergency alarms blared, but there were no immediate reports of injuries or damage in the capital.

Users on Twitter posted pictures and videos of high-rise buildings swaying in Makati City, Manila's business district.

The Philippine National Disaster Risk Reduction and Management Council initially reported a 5.7-magnitude earthquake striking about 18 kilometres east of Castillejos in Zambales province at a depth of 21km. It later raised it to 6.1.

The earthquake struck at 5.11pm local time and was felt in the capital and in the north as far as Urdaneta City in Pangasinian province and as far south as Batangas.

Filipinos were quick to receive text warnings from the disaster authority.

"A 5.7 earthquake just happened in Castillejos, Zambales at 5.11pm," it read. "Damages and aftershock are to be expected. Be ready and make sure to be safe."

Workers in Manila were instructed to leave buildings and the city was experiencing aftershocks.

Angel Tamayo, an engineer working on a building in the Ortigas Centre business district of Metro Manila, told The National that aftershocks meant work was finished for the day.

Transport officials also closed rail operations in Manila and the airport runway was undergoing inspection. Some areas in Luzon island are without electricity, authorities said.

Feliza Villanueva, 21, told AFP she and four colleagues were at work when the earthquake struck.

"This was the second strongest quake I've felt in my entire life," she said, as she joined hundreds of others in the courtyard of an office building, waiting for the all clear.

"We were worried but we did not panic. We planned how to evacuate the building. There were too many people going down the stairs, so we waited for our turn.

"People looked in shock but no one was shouting or anything like that."

Dani Justo, a martial arts instructor, said she was at her Manila home when the quake struck.

"The clothes hanging on our line were really swaying. My shih tzu [dog] dropped flat on the ground," she said.