A cyclone has unleashed heavy rain and strong winds on Bangladesh's coastal region, killing at least five people and forcing hundreds of thousands from their homes to escape the storm's impact.

Local media say the deaths were caused by the collapse of houses in Bhola, Chittagong and Patuakhali districts on Saturday. Cyclone Roanu crossed the southern coastal district of Cox's Bazar and weakened after triggering rains.

The meteorological office said in a statement that dozens of villages have been submerged by floodwaters.

Mohammed Ali Hossain, a government administrator, said nearly 100,000 people were forced from their homes on Moheshkhali island.

Bangladesh, a delta nation, is prone to deadly cyclones.