A strong earthquake, measuring 7.2 on the Richter scale, struck the Nicobar Islands on Sunday night, but there was no immediate report of death or destruction, Met Department sources said.
The epicentre of the quake, experienced at 2112 hours, was Nicobar.
Tremors were experienced as far as Chennai and some other places in south India, but there is no tsunami warning yet, Met sources added.
In Delhi, the Centre said it was not issuing any tsunami alert as that could lead to 'unnecessary panic', but a close watch was being kept on the situation.
A K Bhatnagar, deputy director general of Indian Meterological Department, said in New Delhi that any quake between 7.2 and 7.5 may trigger a tsunami, but there was no rise in sea level in the Andaman and Nicobar islands.
Science and technology minister said in Delhi that there has been 'no unusual activity' in the sea and there was no need to panic.
Andaman and Nicobar Governor Ram Kapse said in Port Blair that there has been no loss of death or destruction in the group of islands.
He, however, said an alert has been sounded across the island and people have been asked to stay away from sea shores.
Union Home Secretary (Border Management) D K Sankaran said, "We do not want to create unnecessary panic by issuing any advisory."
Sankaran added that police and revenue officials in Andaman and Nicobar Islands 'are keeping a close watch on the situation'.
He said the Disaster Management Control room has been activated and would continue to remain in touch with authorities in the Islands and Tamil Nadu.
The quake, however, set off widespread panic among residents in Port Blair who rushed out of their homes and other parts of the islands where an estimated 10,000 people had been killed in the December 26 tsunami in 2004.
The tremors came in the wake of unusually high tide in the sea for the last two days leading to the submerging of many low-lying areas.
After the major quake, which was felt in the entire island range, there were repeated aftershocks mainly in the Nicobar group of islands in the south.
Defence sources in the Car Nicobar islands also said there was no damage at any place although repeated shocks were felt.
An Indian Air Force base is located at Car Nicobar and it had suffered maximum damage in December tsunami in which nearly 100 defence personnel had died.
Even at Katchal island, which lies between Car Nicobar and Campbell Bay and where maximum casualty was recorded after the tsunami, there was no report of any damage.
Official sources said in Port Blair said people in Cambell Bay, which is located in the southernmost end of Andaman and Nicobar islands, were contacted and nothing alarming has been reported from anywhere.
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