(Reuters) - A magnitude 7.3 earthquake struck west of Indonesia's Sumatra Island on Tuesday, Indonesia's geophysics agency (BMKG) said, triggering a tsunami warning.
The European-Mediterranean Seismological Centre (EMSC) earlier pegged the quake at 6.9 magnitude.
The quake, at a depth of 84 kilometres (52.2 miles), triggered an tsunami warning, the country's meteorological department added. The agency asked local authorities to immediately instruct residents of the affected area to move away from shores.
The quake hit at about 3 a.m. local time (2000 GMT). A number of aftershocks were detected later, and some registered around 4 magnitude, BMKG data showed.
Indonesia's disaster mitigation agency said authorities were collecting data from the islands nearest the epicentre off the western shore of Sumatra, spokesperson Abdul Muhari said.
In Padang, the capital of West Sumatra, the quake was felt strongly, and some people moved away from the beaches, said Abdul, who was in Padang.
"People left their homes. Some were panicking but under control. Currently some of them are evacuating away from the sea," he said, adding he had seen no damage so far.
Local news footage showed some Padang residents evacuating by motorbike and foot to higher ground. Some carried backpacks while others huddled together under an umbrella against the rain.
"On the Siberut island, people had already been evacuated. They have been told to stay at the evacuation area until tsunami warning is lifted," Noviandri, a local official told TvOne.
Indonesia suffers frequent earthquakes because it straddles the so-called Pacific Ring of Fire, a seismically active zone where different plates of the earth's crust meet.
(Reporting by Mrinmay Dey in Bengaluru, Fransiska Nangoy and Angie Teo in Jakarta; Editing by Chris Reese, Bill Berkrot and Cynthia Osterman)