Bangladesh and eastern India went on cyclone alert on Wednesday and ships were turned back to port with the storm expected to make landfall in the next two days.

The Bangladesh Meteorological Department said the cyclone with winds of around 185 km (115 miles) per hour was some 850 km (531 miles) off the coast as of 0300 GMT on Wednesday.

He said the storm was expected to hit Vishakapatnam on the eastern Indian coast as well as Sittewe in Myanmar.

The British storm tracking system -- Tropical Storm Risk -- has described the storm as category 4, with windspeeds of up to 250 km (155 miles) per hour.

It was likely to weaken to a category 3 storm by Thursday, losing some speed and ferocity, the TSR said in its latest forecast.

But meteorology officials in Bangladesh said the cyclone could still be very devastating.

Nearly 10 million Bangladeshis live in vulnerable points along the coast, but there are storm shelters for only half a million people, a disaster management official said.

Storms batter the poor south Asian country every year, killing hundreds of people. A severe cyclone killed more than half a million people in 1970, while a 1991 storm killed 143,000 people and destroyed thousands of homes, mostly because of a devastating tidal surge.

"This is a very serious cyclone," said B.P. Yadav, director of the India Meteorological Department, adding that he expected the storm to cross the coast of Bangladesh and the neighbouring Indian state of West Bengal by Friday morning, near Sagar Island.

Operations at Bangladesh's main Chittagong port were suspended and hundreds of ships and fishing boats returned to the shore on Wednesday.

"We have suspended loading and unloading of cargo on the mother vessels at the outer anchorage as the sea has turned turbulent," a port official said.

Many people living on the coastline near Chittagong have begun to vacate their homes, carrying supplies of food, drinking water and other belongings.

Bangladesh's tourists resorts, Cox's Bazar and Kuakata, wore a deserted look on Wednesday and hotels were largely empty, officials and witnesses said.

Volunteers of the Cyclone Preparedness Centre started moving through villages, alerting people on loudspeakers at all vulnerable places.

"A severe storm is coming. Please get ready to move your families to shelters or anywhere away from the shores," one volunteer told villagers at Charkashem in Patuakhali district.

Indian officials said Kolkata, the capital of West Bengal state, should expect to be hit by "squally winds and heavy rainfall". The neighbouring state of Orissa would also be affected.