More than half a million people have been marooned after vast swathes of land were inundated in north-eastern Bangladesh.

Officials said that a district of Sylhet was hit by sudden flooding triggered by heavy rain upstream on Friday.

According to the local administration, the government opened nearly 550 temporary shelters as the flooding affected some 533,202 residents in remote villages and townships in the district.

"We are trying to move the flood-affected people to safety," said Sheikh Rasel Hasan, chief administrator of the district.

He added that some 4,802 villagers were shifted to the shelters in the last couple of days.

The Bangladesh Water Development Board (BWDB) said the major rivers, Surma and Kushiyara, were breaking their banks because of heavy rainfall in the hills across the border.

"The major rivers in the north-eastern region of the country are in a rising trend, which may remain steady in the next 24 hours," the BWDB said in its morning bulletin Friday.

If there is no further rain and a surge of waters from across the border, the situation may improve in seven days, Dipok Ranjan Das, a hydrologist in the district, said.

He said there was no rain reported in Sylhet for Friday.

A 10-day forecast for the overall nationwide situation by the Flood Forecasting and Warning Centre said that water in the major Brahmanputra-Jamuna and Ganges-Padma river systems would continue to decrease.

Natural calamities like flooding and cyclones are common in Bangladesh. A month-long flooding affected an estimated 7.2 million people in nine north-eastern districts in the monsoon of 2022.

A tropical cyclone lashed the Bangladeshi coastline earlier this week, killing at least 13 people and damaging thousands of thatched houses alongside other infrastructure.