JAKARTA—A massive earthquake and strong aftershock rattled Indonesia's westernmost province of Aceh on Wednesday, spurring fears of a tsunami in the same region where a 2004 tsunami killed more than 200,000.

The 8.6-magnitude earthquake was felt as far away as Thailand, Malaysia and India. The Pacific Tsunami Warning Center had issued a tsunami watch Wednesday afternoon in Asia but later canceled it, saying that while a significant tsunami was generated by the quake, the threat for most areas had diminished.

The initial alert said the tsunami watch was in effect from Indonesia to India, Sri Lanka, Australia, Somalia, Oman, Iran, Bangladesh, Kenya, South Africa and Singapore.

 

Indonesian President Susilo Bambang Yudhoyono said that early reports were that there was limited damage. "There is no tsunami threat," he said Wednesday evening ahead of a news conference with British Prime Minister David Cameron. "The tsunami early-warning system is working well and at the moment there are no casualties."

India also canceled its tsunami warnings and alerts for several states and territories, including the Andaman and Nicobar Islands in the Indian Ocean.

In a statement, India's Home Ministry said it had asked the chief secretaries of the Andaman and Nicobar Islands, and all east-coast states, to advise fishermen not to venture out to sea and to take other precautions.

Teams from the National Disaster Response Force were placed on standby in case they were needed to carry out emergency relief efforts, the agency said.

The U.S. Geological Survey said the powerful quake was centered about 20 miles beneath the ocean floor, about 300 miles from Aceh's provincial capital.

Indonesian television news showed crowded roads as people tried to drive away from the coast.

"It felt like the earthquake back when we had a tsunami in 2004," said driver and Aceh resident Edi, who like many Indonesians goes by one name. "Everybody ran around in a panic and we ran up a hill."

People in Banda Aceh screamed "God is great!" as they jumped into cars and onto the backs of motorcycles, clogging streets as they fled to high ground, according to the Associated Press.

Coastal residents in Sri Lanka were told to move to higher ground. Thailand's National Disaster Warning Center issued an evacuation order to residents in six provinces along the country's west coast, including the popular tourist destinations of Phuket, Krabi and Phang-Nga. Thailand later canceled its tsunami warning.

Indonesia sits atop a web of fault lines that makes the sprawling archipelago prone to volcanic and seismic activity. A giant 9.1-magnitude quake off the country on Dec. 26, 2004, triggered a tsunami in the Indian Ocean that killed 230,000 people, nearly three quarter of them in Aceh.

Indonesia's government has improved its monitoring of earthquake data since then by positioning buoys to take sea-level readings and warn of potential tsunamis. Officials have noted the problem of getting timely information to people who live in remote areas of coastal Sumatra.

Experts said the kind of devastation seen in the 2004 disaster and last year in Japan was caused by a particular type of earthquake. During Wednesday's quake, the tectonic plates were likely shifting sideways rather than up and down, leaving less of a chance for the giant waves, said Susanne Sergeant, a seismologist at the British Geological Survey.

"The earthquake today was different from that in 2004 off Aceh and in Japan," last year, and less likely to create massive water displacement, she said.