A 6.9-magnitude earthquake struck off Indonesia's western province of West Sumatra early Tuesday with the potential to trigger a tsunami, forcing thousands of residents to flee coastal areas, officials said.

The earthquake happened at 03:00 a.m. Jakarta time Tuesday (2000 GMT Monday), with the epicenter at 177 km northwest of Mentawai Islands district and a depth of 84 km under the seabed, said the country's meteorology, climatology and geophysics agency.

A tsunami warning was put in place by the agency, which revised the quake magnitude to 6.9 from its initial 7.3.

Over 2,000 residents have fled coastal areas, heading to higher ground in the sub-districts of Siberut Barat (West Siberut) and Siberut Utara (North Siberut) of Mentawai Islands district, said disaster management official Amir Ahmari.