The earthquake jolted the island at 4:48 am (local time) at a depth of 112kilometres, the USGS said.
It was followed by a 5.8-magnitude quake in the same region a few minutes later.
Authorities of Calatagancity in Batangas province, which is south of Manila and near theepicenter of the quakes, said the quake was very strong and theyhad issued a state of alert.
Forces are checking low-lying areas in case there's a tsunami,they added.
Accordingto the US Tsunami Warning System, there was no tsunami warning or threat.
The Philippines lies along the "Pacific Ring of Fire" which is surrounded by numerous activefaults and trenches on both sides of the archipelago. The country has frequentseismic activities and is prone to natural disasters./.