Nearly 2,000 people have been confirmed dead in Andaman and Nicobar islands, ravaged by the killer tsunami waves on Sunday.

The tidal waves were triggered by a massive earthquake off the cost of Indonesia.

Deaths: 2,780 in TN | 120 in Kerala | 73 in AP

Powerful aftershocks measuring six on the Richter Scale rocked the islands in the Bay of Bengal again on Monday at around 06:20 am.

The situation is "very grim" and the toll is likely to rise, a local administration official said.

Also see: 'India not prepared to tackle tsunamis'

The administration was unable to reach the Nancowrie group of islands.

The toll in the Nicobar islands was feared to be "in thousands" but information was hard to come by with radio communications still down, Inspector General of Police S B Deol told PTI.

"You can imagine the situation as the islands are spread over 800 km....the toll will be much higher. We are very apprehensive as we do not know what has happened in Nancowrie group of islands at all," he said.