MANILA, Oct. 30 (Xinhua) -- Nearly 400 aftershocks, ranging from magnitude 1.5 to magnitude 6.1, have rattled Tulunan town, the epicenter of the 6.6-magnitude earthquake that struck Cotabato province in the southern Philippines on Tuesday, said the Philippine Institute of Volcanology and Seismology (Phivolcs) on Wednesday.
The institute said "small- to moderate- magnitude earthquakes are expected to continue to occur in the epicentral area for several days to weeks, some of which may be felt."
"Although the occurrence of another earthquake higher than magnitude 6.6 cannot be discounted, the possibility of it coming from the same source area is low," the institute added.
The institute warned that landslides, rock falls, and other types of mass movements may occur on mountainous or hilly areas. It further warned that "offshore large shallow earthquakes may generate tsunami waves that may inundate nearby shorelines."
National Disaster Risk Reduction and Management Council (NDRRMC) said in an official report that it has so far tallied five deaths from the quake and two missing villagers buried alive in the quake-triggered landslide that police said are presumed dead. At least 394 others were injured, the agency said.
According to the NDRRMC, the strong tremor caused damage to buildings, houses and roads, and affected nearly 1,700 families or nearly 8,500 people.
Tuesday's earthquake is the second to hit Tulunan town in less than two weeks. The town was also the epicenter of the tremor that killed seven people and injured 215 others on Oct. 16.
The Philippines, which lies along the Pacific Ring of Fire, is surrounded with numerous active faults and trenches on both sides of the archipelago. The country has frequent seismic activities, registering quakes everyday, though most are not felt.
Phivolcs records an average of 20 earthquakes a day and 100 to 150 earthquakes are felt per year.