"It felt very strong. We're on the 10th floor of the building, and we felt we were being rocked for about a minute," said Elaine Francisco, an executive with an advertising company.

"We opened the door and prepared to go out, but it ended just when about we were going to go."

The United States Geological Survey said the quake's epicentre was about 72km below the sea bed.

Renato Solidum, chief of the Philippines seismology institute, told the AFP news agency  the quake was felt in varying intensities in suburbs around the capital of 12 million people, as well as in nearby provinces.

The Philippines straddles the seismically active co-called Ring of Fire which encircles the Pacific Ocean.

The last major quake to hit the country in 1990 registered a magnitude 7.7 and killed nearly 2,000 people on the main northern island of Luzon.