India evacuated half a million people as massive Cyclone Phailin closed in on the impoverished east coast Saturday, with winds already uprooting trees and tearing into flimsy homes.

The storm packed gusts of up to 240 kilometres per hour (150 miles per hour) as it churned over the Bay of Bengal, making it potentially the most powerful cyclone to hit the area since 1999, when more than 8,000 died, the Indian weather office said.

"The very severe cyclonic storm Phailin is moving menacingly towards the coast," special relief commissioner for the state of Orissa, Pradipta Mohapatra told AFP.

Authorities said they expected a three-metre (10-foot) storm surge when the eye of the cyclone strikes after nightfall, with torrential rain also threatening floods in low-lying areas.

"I've got faint memories of the 1999 super cyclone," nervous 23-year-old student engineer Apurva Abhijeeta told AFP from the coastal town of Puri, 70 kilometres from state capital Bhubaneswar.

"I dread this Phailin. It's as if the world is coming to an end."

Heavy waves pounded the coast as terrified locals made their way to solid buildings, cramming into packed rickshaws and buses as they travelled. Relief efforts were under way, with free food being served in shelters.

Food stockpiling began earlier in the week as Phailin gathered strength dramatically, with many shops stripped bare before they closed on Saturday afternoon.

In Visakhapatnam, further south on the coast of neighbouring Andhra Pradesh state, fishermen frantically sought to secure their boats while others admired the rough surf.

Large boats could be seen anchored out at sea, while the biggest port in the affected area, in Paradip, has shut down.

An AFP correspondent on the last flight to arrive in Bhubaneswar before the airport shut described how the plane aborted the first attempted landing in shearing winds and pounding rain.

'On a war footing'

Officials put the number of people who have been evacuated from the coastal areas of Orissa and Andhra Pradesh at around half a million.

"Approximately half a million people have been evacuated so far, including 1 lakh (100,000) in Andhra Pradesh," National Disaster Management Agency (NDMA) spokeswoman Tripti Parule told AFP.

Officials in the neighbouring state of West Bengal said hotels along the coast had been told to evacuate while Krishna Ram Pisda, the relief commissioner in Chhattisgarh state, said authorities would empty some of their dams into rivers to avert possible flooding.

Parule said the storm was expected to make landfall at about 8:00 pm (1430 GMT).

The agency's vice-chairman Marri Shashidhar Reddy told a news conference it was one of the biggest evacuations in India's history, and had been aided by improved early warning systems.

"We will be on a war footing," he said in New Delhi.

Authorities were still rushing to get people out of the storm's path, even those who were reluctant to move.

In the seaside town of Gopalpur, which is expected to be one of the worst affected areas, women and children were the first to pack into shelters, schools and public buildings, where they lay on mats.

The Indian Red Cross Society also had disaster response teams ready while the air force, fresh from helping evacuate thousands from floods in the Himalayas in June, flew in food and medical supplies to Bhubaneswar.

Sandeep Rai Rathore, inspector general of the army's National Disaster Response Force, said 1,200 of the unit's troops had been sent to Orissa and a further 500 to Andhra Pradesh.

While the storm is still technically one notch below the most powerful category of "super cyclone", the India Meteorological Department sounded its highest "red alert" on Saturday morning.

Some foreign forecasters believe Phailin, which means "Sapphire" in Thai, is more intense than Indian experts are predicting.

The US Navy's Joint Typhoon Warning Center said gusts could reach as high as 315 kilometres an hour.

Memories of '99

It is set to strike the same coastal area that was hit badly in 1999, a region mostly populated with fishermen and small-scale farmers who live in flimsy huts with thatched roofs or shanties.

It took years for crop yields to recover after soil was contaminated by saltwater during the 1999 cyclone, leaving the state dependent on aid.

That storm had higher wind speeds and a larger storm surge -- six metres -- than being currently predicted by the Indian weather office.

A government report on the 1999 disaster put the death toll at 8,243 and said 445,000 livestock perished.

Authorities have said they are better prepared this time around.

The Orissa government said it was setting a "zero casualty target" in the state of close to 40 million people, and was seeking "100 percent" evacuation of people in the worst-affected areas.

Mahesh Palawat, chief meteorologist at Skymet, India's largest private weather forecaster, said authorities appeared better prepared this time.

"The devastation will be much less than the 1999 cyclone... They had three-four days at their disposal," he told AFP.

Some of the deadliest storms in history have formed in the Bay of Bengal, including one in 1970 that killed hundreds of thousands of people in modern-day Bangladesh.