Cyclone Bulbul made landfall near Sagar Island before moving into Bangladesh, with wind speeds of 75mph causing tidal surges around coastal areas. 12 people have been killed and at least 20 more people injured.
Bangladesh's two biggest ports, Mongla and Chittagong, have closed and flights into Chittagong airport have been stopped for safety reasons. The closure of transport hubs has left thousands of people stranded on islands off the coast, including St Martin's Island.
The disaster management secretary reported that 4,000 mostly mud and tin-built houses had been damaged. In Khulna, the worst-hit district, felled trees blocked roads preventing access to the area.
More than two million people have been displaced to storm shelters. The military have deployed to coastal districts, while tens of thousands of volunteers used loudspeakers to urge people to evacuate.