At least 59 people are known to have died in lightning strikes and landslides caused by severe monsoon storms in India and Bangladesh.
Millions of people have been stranded while emergency workers have struggled to reach those affected, with forecasters warning that the flooding is expected to get worse over the coming days.
In India, Assam state’s disaster management agency said 32 of its 35 districts were underwater as the swollen Brahmaputra River broke its banks, displacing more than three million people.
Bangladesh government officials have described the recent flooding as the country’s worst since 2004.
Syed Rafiqul Haque, a former lawmaker and ruling party politician in Sunamganj district, said the country was facing a humanitarian crisis if proper rescue operations were not conducted.
Heavy rains over the last week have inundated vast swathes of the country’s north-east region, exacerbated by runoff from heavy downpours across mountains in neighbouring India.
Troops were called in to rescue thousands of people stranded by floods which have severed transport links, authorities said on Saturday.
Schools have been converted into makeshift shelters and troops have been deployed to evacuate households cut off from neighbouring communities as a result of rising waters.
Bangladesh and India have experienced increasing extreme weather in recent years, causing large-scale damage.
Environmentalists warn climate change could lead to more disasters, especially in low-lying and densely populated Bangladesh.
