MANILA - An earthquake with a preliminary magnitude of 6.1 hit waters off the southern Philippines on Saturday morning, the Philippine Institute of Volcanology and Seismology said.

The institute said the quake, which occurred at 7:07 am local time (2307 GMT), hit at a depth of 79 km, about 85 km southeast of Sarangani town in Davao Occidental province.

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The institute said the tectonic quake is expected to trigger aftershocks but does not pose a tsunami threat. There is no report of casualties or damage.

The archipelagic Philippines has frequent seismic activities due to its location along the Pacific "Ring of Fire."