(CNN) -- The world's most powerful earthquake in 40 years triggered massive tidal waves that slammed into villages and seaside resorts across Asia on Sunday, killing thousands across five countries.

The quake, near the Indonesian island of Sumatra, triggered giant waves -- or tsunami -- that swept across the region.

Over 1,700 people in Sri Lanka were killed after tidal waves battered the country's eastern coast, according to Colombo police. Authorities fear the death toll there could rise.

At least 1,000 Indians were killed in India as a result of tidal waves which flooded the southern coast, Interior Minister Shivraj Patil said.

Thai authorities say nearly 250 have been killed as a result of tsunamis.

Eyewitnesses in the eastern Sri Lankan port city of Trincomalee reported waves as high as 40 feet, hitting inland as far as half a mile (1 km).

In addition, up to 200 fishermen are missing at sea off the coast of India, officials have told reporters.

Flash flooding in Indonesia has claimed almost 100 lives, and many more deaths are feared in Thailand after huge waves hit the popular tourist resort of Phuket. Government officials say Thailand's toll is already above 50.

At least 14 people are missing in Phuket, where witnesses described "walls of water" as high as 30 feet (10 meters), flooding the streets, absorbing taxi cabs and other vehicles.

One witness said Laguna Beach, where many of the island's major resort hotels are located, was "completely gone."

Thailand's government has evacuated 10,000 people from southern Thailand and declared a state of emergency. The death toll

Six deaths were also reported from Malaysia's Penang island.

The reports suggest the likely total death toll in the region is likely to exceed 1,000.

The quake prompted a series of powerful aftershocks and tidal waves in Sri Lanka, Thailand and Indonesia's Sumatra Island, according to the U.S. Geological Survey's National Earthquake Information Center.

The death toll has reached 94 in Indonesia's Aceh province after flooding from the earthquake hit the region, hospital and local officials told AP.

Malaysia's official Bernama news agency said a tsunami that struck Penang island killed six people.

The initial quake, measuring 8.5 in magnitude, struck off the western coast of Sumatra around 7 a.m. local time (7 p.m. ET) and was followed by at least six moderate to strong aftershocks in the following hours.

The 8.5 quake is the strongest temblor to hit since 1965, according to geophysicist Julie Martinez with the NEIC, which monitors worldwide earthquakes.

In Indonesia's restive Aceh province, early radio reports said nine people died in a flash flood following the earthquake.

"I saw four bodies of kids and five bodies of adults," one resident identified as Mustofa told El Shinta radio, agencies reported. But the toll quickly rose during the day to be near 100.

CNN correspondent Aneesh Raman in Bangkok said eye-witnesses spoke of a "wall of water" bearing down on the beachfronts of the popular resort of Phuket as at least two waves struck.

Raman said Thai officials were evacuating 10,000 people from the area, and there reportedly was "untold devastation".

In India, dead and missing were reported from three coastal districts of Andhra Pradesh state, Chief Secretary Mohan Kanda told reporters.

Te Indian prime minister's office told CNN that the toll was at least 100, while Communications Minister Dayanidhi Maran said the figure was at least 300.

He said the missing fishermen were out in the sea when the tidal wave hit the area. "I have alerted the administration in nine of Andhra Pradesh's 23 districts," Kanda said, AP reported.

Thousands of people fled their homes in the Aceh provincial capital Banda Aceh when the tremor struck, the official Antara news agency said.

Residents in North Sumatra's capital, Medan, reported a strong tremor that caused panic among residents.

"It was quite strong. We ran out of our houses but we're now back inside," said one resident.

The tremor could be felt as far away as India, 1,400 kilometers from the quake center.

An earthquake measuring 6.4 on the Richter scale rattled Indonesia's eastern Papua province in November, killing 29 people in the coastal town of Nabire.

Indonesia, an archipelago of 17,000 islands, lies along the Pacific Ring of Fire where plate boundaries intersect and volcanoes regularly erupt.