Heavy rain submerged large areas of Puri and at least 160 people in the town were injured, many by flying debris. Witnesses said 300 hotels on the town's shoreline were badly damaged with rooms flooded and windows smashed.

In Puri, a teenager was reportedly killed when a tree collapsed on him, while in Nayagarh district a woman died when she was struck by flying concrete. The third casualty was a 65-year-old woman who died of a suspected heart attack after seeking refuge at a cyclone shelter. Other reports put the death toll at eight or nine.

Meteorologists said Fani should weaken in the next 24 hours as it headed inland. However, authorities in the state of West Bengal and the neighbouring country of Bangladesh remain on high alert as the cyclone is expected to reach towns and villages along the banks of the Ganges.

There is particular concern that the winds and rain could cause mayhem in the densely populated coastal districts of Bangladesh.

In Mancheswar, an area of Bhubaneswar, a 31-year-old railway worker gave birth in hospital as the storm raged outside. Doctors safely delivered the baby girl, who was named Lady Fani.

The effects of the cyclone were felt as far away as Nepal, where the government ordered all those attempting to climb to the summit of Everest to return to Base Camp, after high winds wrecked 20 tents.

The Odisha regional government organised the mass evacuation, thought to be the largest in India's history, after weather reports warned of the severity of the storm. It is believed its actions saved thousands of lives.

India's preparations for cyclones have improved due to meteorological advances and lessons learnt from the region's last super-cyclone in 1999, which claimed 10,000 lives.

The authorities in Bhubaneswar closed the airport until further notice and every train running along the coast was cancelled.

The storm hit in the middle of India's six-week general election, with rain forecast in Kolkata forcing political parties to cancel campaign events.

On India's cyclone scale, Fani is the second-most severe, equivalent to a Category 3 hurricane.

Its timing is unusual, according to data from the Meteorological Department. Most extremely severe cyclones hit India's east coast in the post-monsoon season. Over roughly half a century, 23, or nearly 60 per cent of the cyclones, to hit the country were observed between October and December.

Because Fani spent 10 days gathering strength over the sea, it delivered a huge blow when it made landfall.

The 1999 super cyclone reached wind speeds of 260-280 kph, said India Meteorological Department scientist Mrutyunjay Mohapatra.

"This is not as bad," he said.

"Apart from these winds which may cause damage in terms of uprooting small trees in West Bengal and some big trees in Odisha and extensive damage to thatched houses and mud houses ... [and] disruption of power and telecommunication lines," Mohapatra said, "it can also impact the rail and road traffic and also air traffic for some time."

An Odisha official said communications were disrupted in some areas.

Telegraph, London; AAP