A tsunami alert has been lifted after an earthquake with a magnitude of 7.8 hit the Indonesian island of Sumatra.
The quake's epicentre was 204km (127 miles) northwest of Sibolga on Sumatra's coast, at a depth of nearly 48km, the US Geological Survey said.
Three aftershocks were reported in the northern province of Aceh, but there were no reports of casualties.
Indonesia sits on the Pacific Ring of Fire, one of the world's most active areas for earthquakes and volcanoes.
It has recently been struck by a string of quakes; one off Sumatra in September killed more than 1,000 people.
The latest quake - the largest in the area since March 2008 - struck at 0515 on Wednesday morning (2215 GMT on Tuesday).
Although the Pacific Tsunami Warning Center initially said a small tsunami would possibly hit coasts within 100km of the quake's epicentre, a destructive widespread tidal wave was said to be unlikely.
Japan's Kyodo news agency reported blackouts in Medan and Banda Aceh, the capital of Aceh Province.
Local television reported that people rushed to higher ground in some areas.
Thai authorities also warned people in coastal areas to evacuate to a safe place.
In December 2004, a 9.1 magnitude quake off the coast of Aceh triggered a tsunami in the Indian Ocean that killed quarter of a million people in 13 countries including Indonesia, Sri Lanka, India and Thailand.
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