BANDA ACEH, Indonesia - A powerful 8.6 magnitude earthquake and a series of strong aftershocks struck off Indonesia on Wednesday, sending people scurrying from buildings as far away as southern India, but there seemed little risk of a disastrous tsunami as in 2004.

Indonesia said it was checking for damage and casualties but remarkably, no such reports had been received for several hours after the quakes, including in Aceh, the closest province and the area decimated by the disaster eight years ago.

However, some areas close to the epicenter are remote so it could take some time to find out if there was any damage.

Many people were frightened of further tremors.

"It's dark out here but I am scared to go home," said Mila, a 41-year-old woman taking refuge in the grand mosque in the town of Banda Aceh, the provincial capital.

"I just want to stay alert because I fear there will be more quakes coming. We are human, it is only natural that we have fear, but I really wish we will all be safe."

Waves of up to one meter (3.3 feet) high were seen near islands off Aceh, but Indonesia cancelled a warning for fresh tsunamis. It said the worst-hit area was the thinly populated island of Simeulue, off Aceh's southern coast.

The first quake struck at 0838 GMT and an 8.2 magnitude aftershock just over two hours later, at 1043 GMT. Two more strong aftershocks hit later.

The Hawaii-based Pacific Tsunami Warning Center also withdrew tsunami warnings for the entire Indian Ocean after keeping them in force for several hours.

"Level readings now indicate that the threat has diminished or is over for most areas," the agency's bulletin said.

Thailand and India also withdrew tsunami warnings.

Thailand, Indonesia, Sri Lanka and India were all badly hit in 2004. At least 230,000 people in 13 Indian Ocean countries were killed in the Boxing Day disaster that year, including 170,000 in and around Aceh alone.

Last year, an earthquake and tsunami off Japan's northeastern coast killed at least 23,000 people and triggered the world's worst nuclear crisis in 25 years after waves battered a nuclear power station.

On Wednesday, people near the coast in six Thai provinces were ordered to move to higher ground. Authorities shut down the international airport in the Thai beach resort province of Phuket.

The quakes were about 300 miles (500 km) southwest of Banda Aceh, on the northern tip of Indonesia's Sumatra island, the US Geological survey said. The first was at a depth of 20.5 miles (33 km).

Indonesia's disaster management agency said power failed in Aceh province and people were gathering on high ground as sirens warned of the danger.

"The electricity is down, there are traffic jams to access higher ground. Sirens and Koran recitals from mosques are everywhere," said Sutopo, spokesman for the agency.

"The warning system worked," Indonesian President Susilo Bambang Yudhoyono said.

Warning sirens also rang out across the Thai island of Phuket, a tourist hotspot that was one of the worst hit areas in the 2004 tsunami.

"Guests from expensive hotels overlooking Phuket's beaches were evacuated to the hills behind and local people were driving away in cars and on motorcycles. Everyone seemed quite calm, the warning had been issued well in advance," freelance journalist Apichai Thonoy told Reuters by telephone.

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