A huge earthquake just miles away from the centre of the tremor that caused the Boxing Day disaster caused widespread panic across South Asia today over fears that it would unleash a deadly tsunami.

The US Geological Survey (USGS) said that the earthquake, measuring 8.7 on the Richter scale, struck at 1609 GMT off the coast of Sumatra.

The earthquake appeared to have been caused by the same seismic fault as that in December, and to have taken place just a few hundred miles south.

The epicentre was located about 205 kilometres (125 miles) west of Sibolga on Sumatra and 245 km (150 miles) southwest of the Sumatran city of Medan in waters about 30km (18.6 miles) deep.

Hours after the earthquake there were no reports of a tsunami, although on the island of Nias, south of Sumatra, there were casualties. "I can say that tens of people died but I cannot be sure," Agus Mendrofa, the deputy chief of Nias island said.

He said that hundreds of houses had collapsed in the island’s capital Gumung Sitoli. Many were left trapped under buildings as thousands of residents fled to higher ground.

Earthquake monitors around the Asia Pacific region detected the earthquake and scientists urged immediate action in anticipation of a tsunami.

Authorities in India, Sri Lanka, Thailand and Malaysia, who were caught unprepared on Boxing Day, issued evacuation warnings in coastal areas barely recovering from the first disaster.

But it was felt strongly in the northerly province of Aceh, worst hit of all the tsunami stricken regions, where people have become used to aftershocks from the first quake. According to witnesses in the city of Banda Aceh, the tremors lasted for more than two minutes, and people ran from their homes and made for higher ground in anticipation of an incoming wave.

Electricity failed, and live footage broadcast on Japanese television showed roads packed with cars full of fleeing families. In the Malaysian capital, Kuala Lumpur, people ran out of apartment buildings and hotels.

Thai television reported that tourists in the beach resort of Phuket were fleeing for higher ground, where tsunami warnings for six provinces were issued an hour after the latest earthquake. In December Thai officials were criticised for failing promptly to pass on information about the auke for fear of scaring tourists.

The December 26 earthquake measured 9.0 and triggered a tsunami that killed more than 273,000 people around the Indian Ocean.

It was caused when the Indian-Australian tectonic plate slid under the Philippine plate in a "subduction zone" 750 miles long and more than 300 miles wide. The movement was 16½ yards at a depth six miles below the seabed.

Most people across South Asia were already in bed by the time news of the quake began hitting television and radio networks tonight, slowing attempts to get the message out.

In the Andaman Islands, they did not need telecommunications: a massive jolt was felt there within half an hour of the quake, causing panic among traumatised survivors there.

The news from the Andamans, the most easterly Indian territory, prompted the Indian Government to immediately reconstitute the emergency control room they had set up after the first quake.

The Government struggled to get a warning out despite the late hour; in Tamil Nadu, the state worst affected on Boxing Day, appeals were being put out on radio for people to move away from the coastal areas for fear another tsunami could strike within minutes.

By then, on the east coast of Sri Lanka, sirens used to warn people of air strikes during the long civil war there, were being used to try and rouse people from their beds and move in land. Many people living there had already moved back to their destroyed homes close to the coast to restart their fishing livelihoods.

Researchers at the University of Ulster have recently given warning of earthquake and tsunami-related activity in the region.

Their results, published in the March 17 edition of Nature, indicated an increase in the stress on both of the fault zones due to the movement of the initial quake in December.

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