India has issued a red alert as a massive cyclone bore down on the east coast, forcing the evacuation of hundreds of thousands of people, officials said.
Cyclone Phailin was packing gusts as high as 240 kilometres per hour and had the potential to be the strongest storm to hit the area in 14 years, bringing a three-metre surge in sea levels.
High winds and heavy rain were already lashing the state of Orissa and neighbouring Andhra Pradesh, where trees were bent double several hours before Phailin was due to make landfall.
The cyclone is set to hit the same coastal area dotted with flimsy huts and shanties as a storm in 1999 that killed more than 8000 people.
The Indian Meteorological Department issued a so called "red message" warning of the "very severe" cyclone's impending arrival.
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The US Navy's Joint Typhoon Centre said gusts could reach as high as 315 kilometres an hour, while London-based Tropical Storm Risk put Phailin in its most severe "super cyclone" category.
The armed forces have been mobilised to help with relief efforts and the Indian Red Cross Society has put disaster response teams on standby in Orissa, Andhra Pradesh and Andaman Nicobar.
The Orissa government said it was setting a "zero casualty target" in the state of close to 40 million people and was seeking "100 per cent" evacuation of people in the worst-affected areas.
Special relief commissioner for Orissa, Pradipta Mohapatra, said 250,000 people had already been moved out of harm's way.
Satellite photos showed an intimidating cloud mass barrelling across the Bay of Bengal with forecasters saying the danger zone was about 150 kilometres wide.
In Orissa's capital, panic buying saw many shops run low on food.
The 1999 cyclone had higher wind speeds and a larger storm surge - six metres - than being currently predicted by the Indian weather office.
Some foreign forecasters have suggested that India's weather office is underestimating the power of Phailin, however, which means "sapphire" in Thai.
A government report on the 1999 disaster put the death toll at 8243 and said 445,000 livestock perished.
Authorities have said they are better prepared this time around.
Cyclones are a common occurrence in the Bay of Bengal at the end of the steamy monsoon season, when sea temperatures are at their warmest.
A cyclone that struck Bangladesh in 1970 killed hundreds of thousands of people.
