Authorities in India and Bangladesh are struggling to ferry drinking water and dry food to flood shelters as floods continue to wreak havoc in the region.
Authorities in flood-hit Bangladesh and northeastern India have scrambled to provide aid to more than nine million people marooned after the heaviest rains in years killed dozens of people across both South Asian nations, officials have said.
"The flooding is the worst in 122 years in the Sylhet region," said Atiqul Haque, Director General of Bangladesh's Department of Disaster Management, on Monday.
Monsoon rains in low-lying Bangladesh have triggered catastrophic flooding in the northeastern Sylhet administrative division, leaving a quarter of its 15 million population stranded amid fast-rising waters and swollen rivers.
Around 300,000 people have been moved to shelters in Sylhet but more than four million people are stranded near their inundated homes, compounding the challenges for authorities to provide aid, including drinking water and medical supplies.
"The situation is still alarming," Mohammad Mosharraf Hossain, Sylhet division's chief administrator, said.
Media reports said those affected by flooding in remote areas are struggling to access drinking water and food.
"I have never seen such floods in my life," Khalilur Rahman, a resident of Sylhet's Sunamganj district, said.
"Dry food is running out, there is no drinking water."
'The biggest challenge is to provide relief materials'
In the neighbouring Indian state of Assam, where at least 26 people have been killed since heavy rains began around a fortnight ago, flood waters have started receding, authorities said.
But 4.5 million people have been forced from their homes, with around 220,000 staying in makeshift shelters run by the government. Over a million hectare of farmland has been flooded.
"The overall flood situation is improving," Assam's Water Resources Minister Pijush Hazarika told Reuters.
"Now the biggest challenge is to reach out to the displaced people and provide them with relief materials."
The South Asian neighbours have experienced increasing extreme weather in recent years, causing large-scale damage, and environmentalists warn that climate change could lead to more disasters, especially in densely populated Bangladesh.