DAVAO CITY, Aug. 5 (Xinhua) -- A 5.4-magnitude quake struck parts of southern Philippines on Saturday, state seismologists said.

The moderately strong earthquake which occurred at around 8:30 a.m. local time was traced 22 km southeast of Malapatan township, in Mindanao's Sarangani province at a depth of 30 km, the Philippine Institute of Volcanology and Seismology (Phivolcs) said.

Phivolcs said Intensity V was felt in Digos, Davao del Sur, a city of about 150, 000 people, while the regional capital of Davao experienced an Intensity III shaking.

The state seismic bureau said no damage was expected but warned there could be numerous aftershocks.

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