OFFICIALS in Indonesia are today checking for damage and casualties after a powerful 8.6 magnitude earthquake and a series of strong aftershocks prompted panic among millions of coastal residents living around the Indian Ocean.

Despite widespread tsunami alerts no such reports had been received 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 epicentre 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."

Waves of up to 3.3ft 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 Centre also withdrew tsunami warnings for the entire Indian Ocean after keeping them in force for several hours. "Level readings now indicate 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 north-eastern 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.

Yesterday, 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 south-west 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.

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.

Indonesian television showed people gathering in mosques in Banda Aceh. Many others were on the streets. In the city of Medan, a hospital evacuated patients, who were wheeled out on beds and in wheelchairs.

Yesterday's quakes were felt as far away as the Thai capital, Bangkok, and in southern India, office workers in the city of Bangalore left their buildings while the port of Chennai closed down because of tsunami fears.

The quakes were in roughly in the same area as the 2004 quake, along a fault line running under the Indian Ocean, off western Indonesia and up into the Bay of Bengal.

Experts said yesterday's quakes were a "strike-slip" fault, meaning a more horizontal shift of the ground under the sea as opposed to a sudden vertical shift, and less risk of a large displacement of water triggering a tsunami.

"The nature of the sideways rupture and sideways movement is not predisposed to cause a bad tsunami, so almost certainly, the crisis has been avoided," said David Rothery, an expert at the Open University in the UK.

The quakes were also felt in Sri Lanka – where workers in the capital, Colombo, fled their offices.

In Bangladesh, where two tremors were felt, authorities said there appeared to be no threat of a tsunami. Australia also said there was no threat of a tsunami there.