A strong earthquake has been recorded 255km (160 miles) west of the Indonesian island of Sumatra.
The US Geological Survey said the quake measured 6.5 and struck at a depth of 30km (18.6 miles) at 2110 (1410GMT).
There have been no reports of deaths or damage as a result of the earthquake, and no tsunami warning has been issued.
An earthquake in the same region led to a tsunami in December 2004, killing at least 200,000 people in 13 countries. Indonesia was the worst hit.
The US Pacific Tsunami Warning Center said earthquakes of the size recorded on Saturday can generate local tsunamis.
However an official at Jakarta's Meteorology and Geophysics Agency said that more than an hour after the quake, there had been no reports of a tsunami.
The tremor was centred in the ocean about 63km (40 miles) from Sinabang, the main town on the island of Simeulue, Indonesian officials said.
A local journalist in the Sumatra provincial capital Medan told the AFP news agency the tremor was felt "very briefly" and that there was no panic.
It was also felt in the town of Sibolga and on the island of Nias, which in March this year was badly affected in an 8.7 magnitude quake.
Indonesia lies on the Pacific 'Rim of Fire', where the continental tectonic plates meet, causing high volcanic and seismic activity.
Earlier this week, the country activated the initial stage of a tsunami early warning system off the coast of Sumatra which aims to prevent a recurrence of last December's tsunami.