The undersea quake measuring up to 8.7 on the Richter Scale was one of the strongest temblors in 100 years and led India, Malaysia, Sri Lanka and Thailand, among others, to join Indonesia in issuing public warnings of imminent tsunamis.

Alerts rang out on television, radio, by police loud hailer and by alarmed residents ringing bells to tell people in areas devastated by the December 26 tsunamis, caused by a 9.0-magnitude quake also off northwest Indonesia.

Three hours after the quake, Indonesia and Thailand gave the all clear and said it appeared the temblor had not caused any seismic waves. Sri Lanka and India followed several hours later.

However police said at least two deaths and major damage were reported on the island of Nias, around 125 kilometres (77 miles) west of Indonesia's main northern island of Sumatra and close to the epicenter.

The island of 500,000 people was already struggling to recover from the earlier tsunami, which caused widespread damage and left many people without homes and food.

Local officials on Nias said hundreds of houses had collapsed in the capital Gunung Sitoli. Many were left trapped under buildings as thousands fled to higher ground.

"I can say that tens of people died but I cannot be sure," Agus Mendrofa, the deputy chief of the island told Metro Television. "The roads are broken and public facilities were damaged."

The quake brought back fresh memories of the December 26 disaster in which an undersea quake triggered giant waves 15 metres (50-feet) high that sped across the Indian Ocean at speeds of up to 700 kilometres (430 miles) per hour and slammed into 11 countries.

Those waves killed more than 273,000 people including over 220,000 in Indonesia, 30,000 in Sri Lanka, 10,000 in India and 5,000 in Thailand. Over two million people were displaced, and the world pledged over 10 billion dollars in aid.

Governments also pledged to create a high-tech tsunami early warning system for the Indian Ocean by mid-2006 to prevent a repeat of the disaster.

Kerry Sieh, a seismologist with the United States Geological Survey (USGS), said Monday's quake measured 8.7 on the Richter Scale and was one of the five biggest earthquakes in the past 100 years. It struck at 1609 GMT Monday some 245 kilometres (150 miles) southwest of the coast of Sumatra.

Tremors shook many parts of Sumatra for three minutes, witnesses said, and rocked buildings in the neighbouring countries of Malaysia and Singapore where people fled high-rise buildings.

"When the earthquake happened, I rode my motorcycle to the airport because I was very afraid the tsunami would hit again," said university student Heri in Banda Aceh, the capital of Indonesia's devastated Aceh province.

Others tried to reach nearby hills, as the screams of children echoed through streets that were temporarily plunged into darkenss by a power outage.

In northwestern Sri Lanka witnesses said people ran to temples and churches where bells were rung to warn people to run to high ground. In the resorts of southwest Thailand holidaymakers fled hotels as television flashed warnings.

Hundreds of people, with children yanked from their beds and still wearing pajamas, gathered at the town hall on the Thai island of Phuket, sleeping on the lawn and in pickups.

Thai television showed people mounting motorcycles and climbing into pickup trucks as bumper to bumper traffic clogged the streets leaving Phuket's Patong beach.

Shopkeepers scrambled to secure their goods, while fishermen took their boats out to sea in hopes of riding out any possible waves and saving their livelihoods.

In India's Tamil Nadu state radio channels warned people to move away from the ocean. In the town of Kanyakumari, a priest said people started rushing out of their homes as soon as television channels flashed news of the alert.

"People are very tense as they fear that another tsunami is going to hit our coasts. Many of our fishermen have gone to the sea and we are praying for their safe return," Xavier Lawrence, priest of St. Alex's church, told AFP.

The quake caused tsunami alerts as far away as the Indian Ocean island of Mauritius and Madagascar, which is over 4,000 kilometres (2,500 miles) from the epicenter.

And Australia's bureau of meteorology said a 25-centimeter tsunami hit Australia's remote Cocos Island early Tuesday and bigger tidal surges were expected to strike Australia's west coast.

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