A cyclone has flooded coastal villages, blown away thatched roofs and left hundreds of thousands of people without power in southern Bangladesh and eastern India, with at least nine deaths reported.

Dozens of villages in Bangladesh were flooded after flood protection embankments either washed away or were damaged by Cyclone Remal. The storm forced the evacuation of nearly 800,000 people from the country’s vulnerable areas.

In India’s West Bengal state, roofs on thatched houses were blown away while electric poles and trees were uprooted in some coastal districts. Heavy downpours also inundated streets and homes in low-lying areas of the state capital, Kolkata.

Remal weakened considerably after making landfall in Bangladesh’s Patuakhali district early on Monday morning, with sustained 111km/h (69mph) winds. The India Meteorological Department said the cyclone had weakened later in the day and warned of heavy showers over Assam and other northeastern Indian states for the next two days.

The Kolkata airport reopened after being shut on Sunday, and Bangladesh shut down the airport in the southeastern 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.