Television news images showed rescuers in boats ferrying people to safety in West Bengal state, with a state-run hospital in one village completely inundated.

West Bengal Chief Minister Mamata Banerjee told reporters that 26 people had been killed this week, with another 250,000 forced to leave their homes and find shelter.

She accused authorities in neighbouring Jharkhand state of needlessly opening dam sluice gates and releasing the waters that had inundated her state.

"The flooding is man-made," she said, adding she had ordered the border with Jharkhand to be closed for three days in response.

Supriyo Bhattacharya, a member of the ruling coalition in Jharkhand, told AFP that his state had no choice but to ease pressure on the dams.

"Holding back the water could have damaged the dams and led to massive floods in both the states," he said.

"Our government will naturally protect the interests of the people of Jharkhand."

The Damodar Valley Corporation (DVC), which manages dams along the Damodar river that flows through the states, said it had "reduced" the release of water on Friday after rainfall eased.

In West Bengal, railway employee Pradip Maity said most people living in his village of Ghatal had taken shelter in relief camps.

"Boats are now the only mode of transportation in the village," he told AFP.

Typhoon rains cause widespread destruction every year in India, but experts say climate change is shifting weather patterns and increasing the number of extreme weather events.