A massive earthquake struck off the coast of the Indonesian island of Sumatra on Wednesday, triggering a tsunami watch for the Indian Ocean.
The magnitude 8.6 quake struck about 500 kilometers from Indonesia's Aceh province, the U.S. Geological Survey said. It took place at a depth of 33 kilometers.
The Pacific Tsunami Warning Center initially issued a tsunami watch for the entire Indian Ocean, but the watch has been cancelled.
Banda Aceh was devastated by a tsunami resulting from an earthquake in December 2004.
[Updated at 9:04 a.m. ET]Â The Pacific Tsunami Warning CenterÂ has cancelled its tsunami watch in the Indian Ocean.
"Sea level readings now indicate that the threat had diminished or is over for most areas," the center said.
[Updated at 8:34 a.m. ET]Â CNN's Kathy Quiano reports that officials have said about 14 aftershocks have rocked Indonesia after the initial 8.6 magnitude earthquake.
Officials are still telling residents to saying stay away from the coastline.
"We are hearing that many residents are choosing to stay away from their homes and have sought shelter on safer and higher ground," Quiano reported, noting that many of the people had taken part in regular drills given that they are prone to quakes and the devastation caused by the 2004 quake.
[Updated at 8:15 a.m. ET]Â Barry Hirshorn, a geophysicist from the Pacific Tsunami Warning Center, told CNN that while the earthquake was a 8.6 magnitude and is considered large, it could be much different than the 9.0 magnitude quake that hit in 2004. Because theÂ epicenterÂ of this recent quake is also nearly double the distance offshore, it also means that it could be less likely to create a massive tsunami.
Hirshorn added that was also largely in part to how the rupture of the earth took place in this tsunami. Hirshorn explained that the earthquake in 2004 made more of a vertical motion, which would produce larger waves, while this strike-slip earthquake creates more side-to-side motion.
"Tusnami-wise, we are lucky that way, for now," he said.
[Updated at 8:12 a.m. ET]Â Â A spokesperson for the Indonesian president said the situation in the country is under control but he still anticipates that tsunamis may hit the area.
Teuku Faizasyah said right now it is most important to ensure people that they are safe. Search and rescue teams have been deployed.
"What's important is to bring confidence among the people that the government is with them, that we are ensuring their safety," he told CNN.
Tsunami warnings are in place for another hour, he added, saying they will watch the remote areas of the country especially closely.
"We are really waiting to hear from the isolated areas, but hopefully we wont receive any bad news,"Â Faizasyah Â said.
[Updated at 8:01 Â a.m. ET]Â Â Waves were reported at 1-meter (3.3-feet) amplitude offshore in Meulaboh, Indonesia, but in other cities they were reported at about a foot or less, according to the Pacific Tsunami Warning Center.
A series of buoys also measured changes in wave height levels, indicating a tsunami couldÂ occur. Waves are normally small when they are out in the ocean, but are expected to be much higher when they reach the shore.
British Prime Minister David Cameron announced that Britain "stands ready to help if required."
[Updated at 7:44 a.m. ET] An evacuation order has been given by Thailand's National Disaster Warning Center for those along the Andaman coast after the earthquake, according to CNN affiliate MCOT.
The warning center's directorÂ Somsak Khaosuwann "urged people along the sea in the Andaman coastal provinces of Phuket, Krabi, Phang-nga, Ranong, Trang and Satun to evacuate to higher ground," according to MCOT.
MCOT, also known as Thai TV 9, noted that tremors were felt as far as Bangkok.
In the Maldives, some resorts were evacuated in advance of possible waves, according to CNN's Erin Burnett, who was on vacation in the region.
[Updated at 7:23 a.m. ET]Â Shimon Dewan, 35,who Â lives in Dhaka, Bangladesh, said that he was finishing his lunch with work colleagues when they felt the tremors and the office was shaking. They left the office and went outside into the courtyard in front of the building.
He sent in a video to CNN's iReport and said that it was the longest earthquake or tremor he has ever felt, lasting about 30 seconds.
[Updated at 7:09 a.m. ET] There has been a magnitude 8.2 aftershock off the western coast of Northern Sumatra,Â accordingÂ to the USGS. The aftershock was 328 miles south-southwest from Bada Ache, Sumatra inÂ IndonesiaÂ and 659 miles from Kuala Lumpur,Â Malaysia.
[Updated atÂ 6:30 a.m. ET]Â Â Australian seismologist Gary Gibson tells CNN it is less likely that a tsunami will be generated as the earthquake moved horizontally rather than vertically, as happened in 2004.
[Updated atÂ 6:24 a.m. ET]Â Â Indonesia's president says there is no immediate threat of a tsunami from earthquake. He was speaking at a joint press conference in Jakarta with visiting UK Prime Minister David Cameron, ITN's Gary Gibbon tells CNN.
[Updated atÂ 6:18 a.m. ET]Â According to Andaman Nicobar islands disaster-management commissioner Punya Salila Srivastava thereâ€™s NO report of any tsunami generation along the Indian archipelago so far. ]
â€śThereâ€™s no update. Nothing to say more at the moment,â€ť she said.
She told CNN authorities have â€śdowngraded the warningâ€ť to an â€śalertâ€ť in Car Nicobar, the northernmost of the Nicobar region.
[Updated atÂ 5:55 a.m ET]Â The earthquake that struck Wednesday off the west coast of the Indonesian island of Sumatra was downgraded to a magnitude 8.6, the U.S. Geological Survey said.
[Updated at 5:35 a.m. ET]Â The power has gone out in Banda Aceh and residents are moving to higher ground, said Sutopo Purwo Nugroho, a spokesman for the Indonesian National Disaster Management Agency.
The extent of the damage is still being assessed.
In 2004, a 9.1-magnitude underwater earthquake struck off the coast of Sumatra, triggering a tsunami that killed more than 200,000 people in 14 countries. Aceh was one of the worse affected areas.
The tsunami, which washed away entire communities, caused nearly $10 billion in damage and more casualties than any other tsunami in history, according to the United Nations.
Since then, officials have worked to improve warning systems and have carried out drills in the region.
Indonesia is on the so-called Ring of Fire, an arc of fault lines circling the Pacific Basin that is prone to frequent earthquakes and volcanic eruptions.
-Â CNN's Kathy Quiano and Harmeet Shah Singh contributed to this report.