March 28: A massive 8.2 magnitude earthquake struck off the coast of Sumatra tonight close to the point where the December 26 tsunami started.

The quake killed dozens of people and destroyed hundreds of homes in the main town on Nias island, off western Sumatra, a TV channel reported quoting a local government official.

Eastern coastal regions of India, including the Andamans and Tamil Nadu that were devastated by the tsunami, went on alert but until midnight there were no reports of walls of water rising up from the sea.

The latest quake had the potential to cause a ?widely destructive tsunami? and authorities should take ?immediate action?, including evacuating coastlines within 1,000 km of the epicentre, the Pacific tsunami warning centre in Honolulu said.

During the December 26 tsunami, there was no such warning.

The centre reported a small tsunami on the Cocos Islands (see map) in the Indian Ocean. The Cocos lie to the south of the epicentre of the quake.

?There has been no major tsunami observed near the epicentre,? it said. ?There was however a small tsunami observed on the Cocos tide gauge.?

Robert Cessaro, an official of the Honolulu centre, told CNN the quake was likely to have directed any tsunami waves to the south in the direction of Mauritius.

In Indonesia, AFP quoted an official of the meteorological and geophysics centre in Jakarta as saying the quake did not appear to have triggered a tsunami there. Indonesia lost most of the nearly 300,000 that died or went missing in the December 26 tsunami.

In Delhi, as officials held an emergency meeting called by home secretary Dhirendra Singh, the government said scientists had not yet ruled out a tsunami. ?We are not taking any chances,? science and technology minister Kapil Sibal said.

More than 16,000 people were either killed or reported missing after the December 26 tsunami in India.

At 11.30 pm, the home ministry sounded a formal warning to Tamil Nadu, the Andamans, Orissa, Pondicherry, Kerala and Andhra.

In Bengal, coastal districts warned fishermen against going to the deep seas. Residents of some areas of Calcutta and suburbs rushed out of homes after noticing waves in local ponds.

A state-wide tsunami alert was sounded in Tamil Nadu. ?People have been asked to move to safer places, particularly along the coast,? Nagapattinam district collector J. Radhakrishnan said.

Nagapattinam was the worst-hit spot on the mainland when the December 26 tsunami struck. District administrations in Chennai, Cuddalore, Kanyakumari and the nuclear power plant at Kalpakkam also went into precautionary mode.

?A tsunami cannot be ruled out,? a spokesman for the Met office in Chennai said.

The lieutenant-governor of the Andamans, Ram Kapse, told Reuters: ?We have issued an initial warning. If there is any problem, we will evacuate.?

The Andaman and Nicobar Islands lost thousands in the December 26 tsunami and is the closest Indian zone to the epicentre of the quake.

Indonesia?s Metro TV quoted a resident on the island of Nias as saying buildings there were damaged.

?Things are quite bad right now,? the resident said. ?There is much damage. People are running in panic. Many people are also trapped.?

He did not elaborate on what he meant by people were ?trapped?.

Tens of thousands of people across northern and western Sumatra fled their homes and drove or ran to higher ground, TV and residents said.