Officials and newspapers, including the respected The Independent daily, said thousands of people were marooned as rain-triggered floods gushed down from northern parts of the country into the Bay of Bengal.
"The trend in the rise of water levels in major rivers indicated that the situation might worsen further, devouring fresh areas," a Flood Warning Centre (FWC) official told AFP.
He added that water levels at 12 out of 85 points across the country were flowing what is considered the danger mark, but the situation in the northeastern part was improving.
The unofficial death toll since monsoon rains started hammering deltaic Bangladesh in May now stands at 55, with most killed in landslides in the southeastern hill tracts earlier this week. The toll includes four people who have drowned over the past few days, reports said.
Witnesses said areas around the capital Dhaka were also flooded, with water levels rising in the Shitalakhya, Balu and Buriganga rivers.
Run-off from hills in neighbouring India have been blamed by experts for the worsening floods in seven north and northwestern Bangladeshi districts of Gaibandha, Bogra, Rangpur, Lalmonirhat, Nilphamari, Sirajganj and Kurigram.
Some 300,000 residents of the seven districts were marooned, the Independent said, but no official confirmation was available.
Aid for the victims was being distributed by the local administration.
Local officials in Sirajganj district, 105 kilometers (66 miles) northwest of the capital Dhaka, said by telephone that thousands of people had been left homeless and at least 25,000 victims had taken shelter on a highway in Kazipur sub-district after the mighty Jamuna river continued to rise.
It has flooded some 10,000 homes and other structures in 100 villages, they said.
But a disaster management ministry control room official told AFP Saturday that the "situation is not serious" and they were yet to prepare any statistics on losses caused by the calamity.
Water Development Board officials said they recorded a 40-centimetreinch) rise in water levels at the Sirajganj point of the Jamuna river over 24 hours to Friday.
The FWC said due to the continued rise of the Brahmaputra and Jamuna rivers fresh areas of Kurigram, Gaibandha, Bogra, Jamalpur, Sirajganj and Tangail districts could also flood.
The Ganges and Padma rivers were also continuing to rise, it said.
Bangladesh's four-month full monsoon starts in July when the average monthly rainfall varies from 1,194 to 3,454 millimetres (48 to 138 inches).
In 1988 three months of sustained flooding left several hundred people dead and caused millions of dollars in damage, prompting a global call to help Bangladesh develop a long-term flood protection system.
But in 1998 Bangladesh was again ravaged by the worst flood in a century, leaving millions homeless and causing massive damage.
In neighbouring India, floods have also displaced thousands of people, mainly in the northeast which neighbours Bangladesh.