A strong cyclone is now striking the shores of Bangladesh and Myanmar after strengthening into the equivalent of a category-five storm.
195kph (120mph) gusts and heavy rain from Cyclone Mocha could cause severe floods on land near the Bay of Bengal.
There are worries that it could impact Cox’s Bazar, which is home to almost a million people and is the largest refugee camp in the world.
Up to four meters of storm surge could saturate low-lying towns.
Cyclone Mocha, according to forecasters, might be Bangladesh’s strongest cyclone in nearly two decades.
About 500,000 people have been evacuated to safer locations.
The Bangladeshi meteorological department office said the maximum sustained wind speed within around 75km (45 miles) of the centre of the cyclone was around 195 kilometres (120 miles) per hour with gusts and squalls of 215 kilometres per hour.
In preparation nearby airports were shut, fishermen ordered to suspend their work and 1,500 shelters were set up as people from vulnerable areas were moved to safer spots.
Cyclone Mocha was predicted to bring a deluge of rain, which can trigger landslides – a serious danger for those who reside in hillside camps, where landslips are a regular phenomenon.
Particular concerns have been expressed for the many Rohingya refugees living in makeshift homes in the the camps of Cox’s Bazaar and people on the western coast of Myanmar.
“For a cyclone to hit an area where there is already such deep humanitarian need is a nightmare scenario, impacting hundreds of thousands of vulnerable people whose coping capacity has been severely eroded by successive crises,” UN Humanitarian Coordinator A.I. Ramanathan Balakrishnan said.