Indonesian officials have issued a tsunami warning after a powerful, shallow earthquake hit off the western coast of Sumatra.
The US Geological Survey (USGS) said the earthquake had a preliminary magnitude of 7.9.
It was centred under the sea at a depth of 6.2 miles.
Shallow earthquakes are more apt to cause damage, but the USGS said the quake was located quite far from land, about 411 miles from Muara Siberut.
A major quake off Indonesia in 2004 triggered a tsunami that killed 230,000 people in a dozen countries. Most of the deaths were in Aceh province.
Australia's Bureau of Meteorology issued a marine warning for the distant Cocos and Christmas islands.
It did not advise evacuations, but said strong and dangerous currents were possible and people should secure boats and avoid waterfront areas.
The warning noted that a tsunami had not been confirmed.