DAVAO CITY, the Philippines, April 12 (Xinhua) -- A earthquake measuring 6.0 on the Richter scale struck parts of southern Philippines on Wednesday, state seismologists said.

The quake which hit around 5:21 a.m. local time was traced 6 kilometers east of Wao town, in Mindanao's Lanao del Sur province at a depth of one kilometer, the Philippine Institute of Volcanology and Seismology said.

The U.S. Geological Survey pegged the quake's strength at magnitude of 5.6.

There were no immediate reports of damage, but the Philippine Institute of Volcanology and Seismology said the temblor is expected to cause aftershocks.

It said shaking was felt in the cities of Davao, Cagayan de Oro and Cotabato.

Wednesday's quake came after a series of temblors, one measuring 6.0, rocked the main island of Luzon on Saturday, destroying several buildings and other structures.

The Philippines sits on the so-called Pacific Ring of Fire where continental plates collide, causing frequent quakes and volcanic activities.