Mass evacuations before Cyclone Sitrang made landfall on the west coast helped save lives but the full extent of the casualties and damage would only be known after communications are restored, they said.
The cyclone barrelled in from the Bay of Bengal early in the day with winds gusting up to 88kph and a storm surge of about 3m that flooded low-lying coastal areas.
Power and telephone links have been largely cut and coastal areas plunged into darkness, officials said.
Most of the people killed were crushed by falling trees.
No major damage was reported in refugee camps in southeast Bangladesh, where more than a million ethnic Rohingya refugees from neighbouring Myanmar are living in flimsy shelters.
Officials advised nearly 33,000 Rohingya refugees who have moved from the camps to a flood-prone island in the Bay of Bengal to stay indoors.
Heavy rain fell on the streets of the capital, Dhaka, causing some flooding and disruption to commuters.
The cyclone also affected the eastern Indian state of West Bengal.
South Asia has experienced increasing extreme weather in recent years causing large-scale damage.
Environmentalists warn that climate change could lead to more disasters, especially in places like densely populated Bangladesh.
Farah Kabir, Bangladesh country director of ActionAid group, said 2022 had seen climate emergencies such as floods and droughts “on a scale that has never been witnessed before”.
“The climate crisis is growing, and here in Bangladesh we feel its ferocity,” he said.
“When extreme weather events like Cyclone Sitrang strike, communities are left devastated. We urgently need access to funds that support communities living through the reality of the climate crisis.”
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