Dubbed a Super Cyclone, Cyclone Mocha is set to hit the coasts of Myanmar and Bangladesh midday today with winds up to 240 kph as both countries rush to protect their citizens.
For the Rohingya refugees living in flimsy shelters in camps in Bangladesh the threat is frightening.
Bangladesh authorities have banned Rohingya refugees from constructing concrete homes, fearing it may incentivise them to settle permanently rather than return to Myanmar, which they fled five years ago following a brutal military crackdown.
"We live in houses made of tarpaulin and bamboo," said refugee Enam Ahmed, at the Nayapara camp near the border town of Teknaf.
"We are scared. We don't know where we will be sheltered."
The camps are generally slightly inland, but most of them are built on hillsides, exposing them to the threat of landslides.
Forecasters expect the cyclone to bring a deluge of rain, which can trigger landslips.
Officials moved to evacuate Rohingya refugees from "risky areas" to community centres and more solid structures such as schools, but Bangladesh's deputy refugee commissioner Shamsud Douza told AFP: "All the Rohingya in the camps are at risk."
Hundreds of people also fled Saint Martin's island, a local resort area right in the storm's path, with thousands more moving to cyclone shelters on the coral outcrop.
"Cyclone Mocha is the most powerful storm since Cyclone Sidr," Azizur Rahman, the head of Bangladesh's Meteorological Department, told AFP.
That cyclone hit Bangladesh's southern coast in November 2007, killing more than 3,000 people and causing billions of dollars in damage.
Rohingya living in displacement camps inside Myanmar were also bracing for the storm.
"We are very worried. We can be in danger if the water level increases," said a camp leader near Kyaukphyu in Rakhine state, who asked not to be named for fear of repercussions from the junta.
"There are about 1000 people at the camp... The authorities only gave us rice bags, oil and five life jackets. Local authorities haven't arranged any place for us."
Operations were suspended at Bangladesh's largest seaport, Chittagong, with boat transport and fishing also halted.
Cyclones - the equivalent of hurricanes in the North Atlantic or typhoons in the Northwest Pacific - are a regular and deadly menace on the coast of the northern Indian Ocean where tens of millions of people live. In 2008, Cyclone Nargis caused massive devastation and killed over 130,000 people.
AFP
