Manila, Sep 26 : An offshore earthquake with a preliminary magnitude of 6.6 rocked the Davao Occidental province in the southern Philippines on Tuesday, authorities said, adding that there was no threat of a tsunami.

The Philippine Institute of Volcanology and Seismology said the quake, which occurred at 9.39 a.m., struck at a depth of 122 km, about 434 km southeast of Balut Island in Sarangani town, reports Xinhua news agency. 

The institute said the tectonic quake will trigger aftershocks but will not cause damage.