Cyclone Mora destroyed thousands of makeshift homes and refugee camps housing Muslim Rohingya refugees on Wednesday in Bangladesh.
At least seven people were killed and 50 injured by Cyclone Mora, according to Mohammad Ali Hussain, the chief administrator of Cox's Bazar district, a sliver of land in southeast Bangladesh bordering Myanmar.
"Almost all rickety houses in the district were completely or partially destroyed by the cyclone. Not only Rohingya houses," Hussain said.
The chief administrator said 17,500 houses had been completely destroyed and 35,000 partially damaged in the district.
The border area hit by the cyclone is home to refugee camps for Muslim Rohingyas who have fled from their homes in northwest Myanmar to escape communal violence and Myanmar army crackdowns.
"Initial reports suggest damage to shelter in camps sheltering Rohingya refugees, is severe," the Office of the UN Resident Coordinator for Bangladesh said.
Authorities in Cox's Bazar and neighbouring Chittagong district evacuated 350,000 people from low-lying areas before the storm roared in from the Bay of Bengal on Tuesday.
But most Rohingyas remained in their shelters in the camps when the storm struck, with priority given to evacuating only the most vulnerable, like heavily pregnant women.
"We have passed a difficult time. We had no tin or plastic sheets above our heads and almost all of us passed the night in the rain," said Omar Farukh, a community leader in Kutupalong camp.
"We tried to save our belongings, whatever we have, with pieces of plastic sheet." he said.
Farukh said aid agency officials had visited the Kutupalong camp to see what was needed.
A relief worker who had visited the Balukhali camp estimated that one in four huts there had been damaged but there were no serious injuries, and people had begun repairs.
A senior UN official working in Cox's Bazar said there had been no reports of deaths in the camps, only some injuries.
Beyond the camps, officials were also assessing the damage elsewhere in Cox's Bazar.
The Bangladeshi government has estimated that in all, there are about 350,000 Rohingyas in Bangladesh following a new influx last October when the Myanmar army launched an offensive in response to insurgent attacks.
The cyclone formed after monsoon rains triggered floods and landslides in Sri Lanka, off India's southern tip, killing 202 people in recent days, authorities said, adding 96 people were missing.
An Indian navy boat rescued 33 Bangladeshis at sea off Chittagong, and recovered one body, the Indian mission in Dhaka said.
Further south, 10 fishermen were rescued and taken to hospital on the island of Kutubdia, said Sojan Chowdhury, officer-in-charge at the island's police station.
Over 130 fishermen and nine fishing boats are still missing, Mostaque Ahmed, head of the Cox's Bazar Mechanised Fishing Boat Owners Association, said.
Transport and communications were in chaos in northwest Myanmar, state media there said.
The cyclone lost some of its force as it moved inland and across the eastern border into India.
Strong wind and heavy rain battered houses, brought down electricity lines, and damaged telecommunication towers in India's Mizoram state, cutting communications and power.
The Meteorological Department said the weather system was very likely to continue to move north to northeast and weaken into a cyclonic storm and later into a depression.
Other northeastern Indian states had received heavy to very heavy rainfall since Tuesday evening.