The triple-decked ferry, the MV Nasrin-1, had been travelling from the Bangladeshi capital, Dhaka to Lalmohan when it hit turbulent waters near the town of Chandpore just before midnight.

Initial reports suggest the ferry may have been overcrowded, not just with passengers, but also with a big cargo of rice and vegetables.

Bangladeshi shipping minister, Akbar Hussein, said around 200 people had managed to swim to shore.

"I think about another four hundred people are still in the ferry," he told the BBC.

"The ferry capsized in a river which has a tremendous current."

Passenger lists

Chandpore is where three rivers, Padma, Meghna and Dakatia merge.

Many of the survivors swam to safety at a nearby ferry terminal, but one of them is reported to have died there.

Others were rescued by local fishermen and other ferries in the vicinity.

A search is under way for those still missing, but rivers are swollen with heavy monsoon rains, making the task of rescuers difficult.

Dhaka's senior river transport official, Abul Hossain Chowdhury, said the ferry had an official capacity of 429 passengers, but was "definitely overcrowded".

It is unlikely that the exact number of passengers on board will ever be known as ferries in Bangladesh rarely have passenger lists or issue tickets.