Media playback is unsupported on your device Media caption An earthquake hits the Philippines island of Luzon

A powerful earthquake has struck the main Philippines island of Luzon, killing at least 11 people.

The magnitude 6.1 tremor hit at 17:11 local time (09:11 GMT) on Monday, the Philippines Institute of Volcanology and Seismology reports.

An airport was seriously damaged and at least two buildings were destroyed.

Less than 24 hours later, a second powerful earthquake measuring 6.4 struck further south, in the central Visayas region.

A BBC correspondent in Manila said the worst hit areas include Tacloban City, Leyte, and Catbalogan City in Samar. Social media posts on Tuesday showed buildings swaying and large cracks forming in roads, but it was not clear if there were any casualties.

Tacloban City and the surrounding region were devastated by Typhoon Haiyan in 2013.

Following the first earthquake, authorities said dozens of people could still be trapped underneath a collapsed building in the province of Pampanga, north-west of the capital Manila.

The province is believed to be the worst-hit area. Its governor, Lilia Pineda, told Reuters news agency that 20 people had been injured there.

"They can be heard crying in pain," she said of those trapped under the rubble. "It won't be easy to rescue them."

Ms Pineda told ABS-CBN television that three bodies had been pulled out of a shop following the earthquake, while a woman and her grandchild were found dead in the town of Lubao.

Twenty people have so far been rescued and taken to hospital, she added.

The earthquake was felt in Manila, where skyscrapers were seen swaying for several minutes in the business district.

Clark International Airport, located about an hour's drive north of the capital, suffered major damage, with at least seven people injured.

Image copyright EPA Image caption People evacuate a building in Manila

Martial arts instructor Dani Justo recalled the moment she felt the earthquake at her Manila home.

"The clothes hanging on our line were really swaying. My shih tzu (dog) dropped flat on the ground," she told AFP.

Social media users on the northern island posted photos of the damage caused by the quake, including cracked walls and swinging light fixtures.

One video posted to Twitter showed water cascading down the side of a skyscraper from its rooftop pool.

Classes at Manila's De La Salle University are being suspended on Tuesday while building inspections are conducted.

The Philippines is part of the Pacific "Ring of Fire" - a zone of major seismic activity which has one of the world's most active fault lines.