The Indonesian government said it received no reports of casualties or significant damage from the initial earthquake, registering 8.6 in magnitude, or from several aftershocks, the strongest of which was 8.2-magnitude, the U.S. Geological Survey said.
The earthquake was felt in Bangladesh, India, Malaysia, Singapore and Thailand, as coastal areas of southern Thailand and eastern India issued tsunami alerts and Indonesia posted a tsunami warning following the aftershocks, The New York Times reported.
The Pacific Tsunami Warning Center canceled its tsunami watch for the entire Indian Ocean after sea-level readings indicated "the threat has diminished or is over for most areas."
"Danger to boats and coastal structures can continue for several hours due to rapid currents," the center cautioned.
Indonesian President Susilo Bambang Yudhoyono told reporters during a news conference in Jakarta the earthquake stirred "a little bit of panic."
In Aceh, in northern Sumatra, the earthquake knocked out electricity and disrupted cellphone service, officials said. Residents in the area were evacuated to higher ground.
On the Andaman and Nicobar Islands, officials and hotel managers told the Times they felt the earthquake, but saw no sign of a tsunami or large waves two hours later.
Deepika Mandal, an employee at the Fortune Resort Bay Island hotel in Port Blair, the capital for Andaman and Nicobar Islands, said the sea was "absolutely calm."
Gary Gibson from the Seismology Research Center in Melbourne, Australia, said the earthquake may have moved horizontally rather than vertically, so it was less likely to generate a tsunami, CNN reported.
Gibson also said the earthquake occurred well offshore and was unlikely to have caused much damage.
In 2004, a 9.1-magnitude underwater earthquake off Sumatra's coast triggered a tsunami that killed more than 200,000 people in 14 countries.