The 6.7-magnitude quake that struck the Mindanao region mid-afternoon on Friday caused part of a shopping mall ceiling to collapse, triggered power cuts and sent people fleeing into the streets.
Falling debris from the mall in General Santos City crushed a woman to death, city police captain Ari Noel Cardos told AFP.
Police earlier reported the death of a couple pinned under a collapsing concrete wall in General Santos.
Another person was killed by a falling steel structure in the municipality of Glan, in Sarangani province, police officer Paul Mesalido told AFP.
Firemen dug with shovels as they searched on Saturday for two members of a family feared buried beneath a landslide at a remote mountain village about four hours’ drive from Glan, rescuer Daniel Nocos told AFP.
“The village chief reported to us that a mother and her child were trapped beneath the rubble,” Nocos said.
An excavator had been sent to help in the search but had not yet reached the area because of bad roads and a damaged bridge, he said.
The official National Disaster Risk Reduction and Management Council in Manila reported a second death in Glan and another in the adjacent Malapatan municipality but gave no details.
In neighbouring Davao Occidental province, an elderly man was killed by a large rock that rolled down a hill near his house, police officer Patrick Laurente said.
Two people were injured in General Santos, while 450 others were treated for panic and breathing difficulties, the disaster agency said.
The quake damaged 60 houses in four provinces as well as 32 roads and bridges in the region, rescuers said.
The state seismology service said the quake was likely generated by the movement of the earth’s crust along the Cotabato trench, a long, narrow depression on the seafloor that forms the boundary of one tectonic plate pushing against another.
Quakes are frequent in the Philippines, which sits along the Pacific “Ring of Fire”, an arc of intense seismic as well as volcanic activity that stretches from Japan through Southeast Asia and across the Pacific basin.
Most are too weak to be felt by humans.