Cyclone Mora battered Bangladesh on Tuesday, killing two people, ripping through camps housing Rohingya refugees and forcing 450,000 people to flee coastal villages.
Police said a woman and a man had been crushed under trees felled by winds of up to 135 kilometres (84 miles) per hour in the coastal district of Cox's Bazar, which bore the brunt of the cyclone.
The district is home to 300,000 Rohingya refugees, most of whom live in flimsy makeshift camps after fleeing persecution in neighbouring Myanmar.
Community leaders said damage to the camps was extensive and there had been no attempt to evacuate the Rohingya. They described how residents had to run for shelter in the middle of the night.
"In some places, almost every shanty home made of tin, bamboo and plastics has been flattened," said Abdul Salam, a Rohingya community leader, adding that around 20,000 houses had been damaged and some residents injured.
Cox's Bazar has for years been home to hundreds of thousands of Rohingya, a stateless minority living mostly in Myanmar.
Their numbers have swelled since a brutal crackdown last October by the Myanmar military sent 70,000 fleeing across the border into Bangladesh.
Away from the camps, authoritieshad evacuated more than 449,000 people to cyclone shelters after raising the highest number 10 weather danger alert as the storm approached. They had initially planned to make one million people leave their villages.
"They have been evacuated to at least 400 cyclone shelters, schools and government offices in the coastal areas," said Golam Mostofa, the senior official coordinating the evacuation.
Cyclone Mora comes days after heavy rains in Sri Lanka killed at least 183 people, many of them buried under landslides, and brought the worst flooding the island has seen in 14 years.
South Asia is frequently hit by flooding in the summer with the arrival of the annual monsoon rains. On Tuesday they hit the southern Indian state of Kerala, from where the will sweep across the country over the coming months.
Mohammad Anam, a Rohingya who fled to Bangladesh last year after an outbreak of violence in Myanmar, said there had been no attempt to evacuate the minority community, many of whom are undocumented.
"Nobody came to alert or evacuate us. When the storm came we rushed to local schools to take shelter," he told AFP.
He said some Rohingya had found refuge in local schools and mosques, but thousands had been left without food or shelter.
Another refugee, Ali Zahar, said roofs had been blown off houses, a school and the office of the camp where he lived.
Anwarul Naser, a senior district official, said several thousand houses had been damaged in the area, most of them mud-built structures.
Zahir Ali, who lives in a camp for unregistered refugees, described how they rushed through the hilly terrain in the dark to take shelter in a nearby mosque as winds and a downpour pounded their houses.
"Many including women and children were injured as they tried to run down the slippery hills to take shelter," Ali told AFP.
The weather office said the cyclone could unleash a five-foot-high (1.7 metre) storm surge around Cox's Bazar, Chittagong and several other coastal districts on the Bay of Bengal, which are home to millions of people.
Authorities called in all fishing vessels and all flights were suspended to and from airports in Chittagong and Cox's Bazar.
Bangladesh is routinely hit between April and December by severe storms that cause deaths and widespread damage.
In May last year Cyclone Roanu hit the southern coast of Bangladesh, leaving 20 people dead and forcing half a million to flee their homes.
In 2007 Cyclone Sidr killed nearly 4,000 people and caused damage worth billions of dollars.
Flash floods and torrential rain led to landslides in hilly areas, which caused most of the casualties.
"But this time we are more prepared," said disaster management authority spokesman Abul Hashim.
In neighbouring India, the National Disaster Management Authority advised fishermen in the eastern coastal state of West Bengal bordering Bangladesh to stay in port.
Weather authorities warned of strong winds and heavy rain across much of northeast India, although the cyclone was expected to weaken as it crossed the country.