A cyclone has flooded coastal villages, blew away thatched roofs and left hundreds of thousands of people without power in southern Bangladesh and eastern India.

At least seven deaths as a result of the cyclone have been reported.

Dozens of Bangladeshi villages were flooded after flood protection embankments either washed away or were damaged by the storm surge, TV stations reported. Nearly 800,000 people had been evacuated from vulnerable areas in Bangladesh on Sunday.

Authorities have given no casualty figures yet, but Dhaka-based Somoy TV reported that at least seven people died. Two others were missing in a boat capsizing, the station said.

In India’s West Bengal state, roofs on thatched houses were blown away while electric poles and trees were uprooted in some coastal districts. There were no immediate reports of deaths. Heavy downpours also inundated streets and homes in low-lying areas of Kolkata city.

Cyclone Remal weakened considerably after making landfall in Bangladesh’s Patuakhali district early in the morning with sustained 69mph winds. The Meteorological Department in Dhaka said the winds were now 56mph with gusts to 75mph.

The India Meteorological Department said Remal was likely to weaken further throughout the day. It warned of heavy showers over Assam and other north-eastern states for the next two days.

The Kolkata airport reopened after being shut on Sunday, and Bangladesh shut down the airport in the south-eastern city of Chattogram and cancelled all domestic flights to and from Cox’s Bazar. Loading and unloading in the Chittagong seaport was halted and more than a dozen ships moved from jetties to the deep sea as a precaution.

Volunteers helped Bangladesh’s hundreds of thousands of evacuees move to up to 9,000 cyclone shelters. All schools in the region were closed until further notice.

Remal was the first cyclone in the Bay of Bengal ahead of this year’s monsoon season, which runs from June to September.

India’s coasts are often hit by cyclones, but changing climate patterns have increased the storms’ intensity, making preparations for natural disasters more urgent.