MANILA: An earthquake with a preliminary magnitude of 6 rattled a southern Philippine region as people slept, collapsing the walls of three houses and injuring at least three people, officials said.

Renato Solidum of the Philippine Institute of Volcanology and Seismology said the early Thursday earthquake was centered under the sea northwest of Zamboanga del Norte province, adding the quake wasn't strong enough to trigger a tsunami.

Police Superintendent Luisito Magnaye said the quake caused the walls of three houses to collapse in a village in Zamboanga city, injuring at least three residents, who were taken to a hospital. Another house was slightly damaged in the rural area.

The Philippine archipelago lies in the Pacific "Ring of Fire," where earthquakes and volcanic activities are common.

A magnitude 7.7 quake killed nearly 2,000 people on the northern island of Luzon in 1990.