Originally Posted by CNN

-- Massive tsunamis triggered by the largest earthquake to shake the planet in over 40 years have wiped out coastal areas across southeastern Asia, killing more than 4,800 people -- most of them in Sri Lanka and India.

The initial quake, measuring 8.9 in magnitude, struck about 100 miles (160 km) off the coast of Indonesia's Sumatra island around 7 a.m. Sunday (0000 GMT), according to the U.S. Geological Survey's National Earthquake Information Center.

It is the fifth largest earthquake in recorded history, according to the NEIC.

Sri Lankan military authorities are reporting over 2,400 people killed, most of them in the eastern district of Batticaloa. Several districts in the country's south have still not reported casualty figures, and authorities fear the death toll could rise.

Officials, however, said thousands were missing and more than a half million had been displaced.

The huge waves also swept away a high security prison in Matara, in southern Sri Lanka, allowing 200 prisoners to escape. Eyewitnesses in eastern Sri Lankan port city of Trincomalee reported waves as high as 40 feet (12 meters), hitting inland as far as half a mile (1 km).

Sri Lankan officials imposed a curfew as night fell, and tourists were being evacuated from the eastern coasts to the capital, Colombo, unaffected on the west coast.

India has agreed to help assist Sri Lanka, sending two naval ships to the resort town of Galle, in the south, and Trincomalee, according to Colombo officials. Indian aircraft will bring in relief supplies to the country on Monday.

India itself is reeling from the aftermath of the quake and tsunami. Indian officials said at least 1,800 Indians were killed as a result of the massive waves. A resident of Chennai (formerly Madras) in Tamil Nadu district -- the hardest hit area -- said he witnessed several people being swept away by a tidal wave there.

Along India's southeastern coast, several villages appeared to have been swept away, and thousands of fishermen -- including 2,000 from the Chennai area alone -- who were out at sea when when the massive waves swept across the waters have not returned.

Along the coast, the brick foundations of village homes were all that remained.

Interior Minister Shivraj Patil told CNN 700 people were killed in Tamil Nadu state and 200 in Andhra Pradesh. Poor communications with India's remote Andaman and Nicobar islands, which were closer to the quake's epicenter, has prevented any reports of damage and casualties. Most of the aftershocks have been centered off those islands.

Thai authorities say more than 250 are feared dead, and hundreds are missing. One witness said Phuket's famed Laguna Beach resort area is "completely gone." The area provides 40 percent of Thailand's $10 billion annual tourist income.

Among the missing were a number of scuba divers exploring the Emerald Cave off Phuket's coast.

Phuket's airport, which closed down when its runways flooded, reopened, but most roads remained closed, as officials tried to assess the damage, fearing structural damage to buildings closer to the shore.

Thai Prime Minister Thaksin Chinnawat arrived in Phuket and said the situation was "under control." He told CNN he planned to stay the night and direct rescue and relief efforts.

Over 500 people were killed Indonesia by the quake and the following tsunamis -- many of them in Aceh, in northern Sumatra, about 100 miles from the quake's epicenter, according to local reports.

"We still haven't got any reports from the western coast of Aceh, which is closest to the epicenter so officials are bracing themselves for a lot more bad news," said journalist John Aglionby in Jakarta.

The earthquake is classified as "great" -- the strongest possible classification given by the NEIC.

NEIC geophysicist Don Blakeman said all of the tsunamis were triggered by the initial quake. Waverly Person, Blakeman's colleague at NEIC, said the tsunamis are "long over at this point," and residents and visitors should not be concerned with more high water.

One major aftershock, measuring 7.3 in magnitude, struck about 200 miles (300 km) northwest of Banda Aceh -- on Sumatra's northernmost tip -- over four hours after the initial quake, according to the NEIC. The rest of the aftershocks measured under 6.5 in magnitude.

The NEIC expects the quake to produce hundreds of smaller aftershocks, under 4.6 magnitude, and thousands smaller than that.

"A quake of this size has some pretty serious effects," he said.

He explained the quake was the energy released from "a very large rupture in the earth's crust" over 600 miles (1,000 km) long. The rupture created shockwaves that moved the water along at several hundred miles per hour.

It was the strongest earthquake to hit since March 1964, when a 9.2 quake struck near Alaska's Prince William Sound. The strongest recorded earthquake (since 1899, when such measurements began) registered 9.5 on May 22, 1960, in Chile.

Sunday's earthquake is the fifth strongest in that period.