In the neighboring Indian state of Assam, at least 17 people have died in a wave of floods that began this month, police said on Sunday.
Many rivers in Bangladesh have risen to dangerous levels and the outflow of heavy rain from the Indian mountains has exacerbated the situation, they said. Arifuzzaman Bhuiyanhead of state Flood forecasting and Alert Center.
Thousands police officersArmy personnel have been deployed in parts of the country to support search and rescue efforts.
About 105,000 people have been evacuated so far, but police estimate that more than four million are still trapped.
Sayed Rafikul Hake, a former MP and politician from the ruling party in Sunamanj district, said the country is facing a humanitarian crisis if appropriate rescue operations are not carried out.
“Almost the entire Sylhet-Sunamganj belt is under water and millions of people are blocked,” he said, adding that the victims had no food, no drinking water and no communication networks.
Regional officials said about 3.1 million people have been displaced, 200,000 of whom remain in makeshift, government-run shelters on raised embankments or other mountains.
Bangladesh and India have been experiencing increasing extreme weather conditions in recent years, causing extensive damage.
Environmentalists warn that climate change could lead to more disasters, especially in low-lying and densely populated Bangladesh.