MANILA - TWO strong earthquakes hit the main Philippine island of Luzon on Saturday but there were no immediate reports of casualties or damage, government seismologists said.

The first quake, with a magnitude of 5.3, struck at about 11.05am and was followed a few minutes later by a stronger quake with a 6.5 magnitude, said Dr Renato Solidum, director of the Philippine Institute of Vulcanology and Seismology.

'The quakes originated deep in the ground and when it reached the surface, it was not that strong,' Dr Solidum said in a radio interview as he minimised the threat.

The quakes were felt in the capital Manila and surrounding areas where they set objects swaying.

Dr Solidum said the quakes were tectonic in origin and had an epicentre off the coast of Mamburao town on the island of Mindoro, just south of Luzon. There was no tsunami warning issued, he added.

In a preliminary report, the US Geological Survey measured the tremors at 6.1 and 5.6 at a depth of 82 and 77 kilometres underground respectively.

The archipelago nation, made up of more than 7,000 islands, sits on the Pacific 'Ring of Fire' where continental plates collide, causing frequent seismic and volcanic activity. -- AFP