At least 29 people were confirmed dead in Bangladesh after a ferry carrying about 150 passengers collided with another vessel and sank on Thursday, a police official said.
The ferry capsized in the Buriganga River just south of the capital Dhaka, said police official Nazmul Hossen, adding that 29 bodies had been recovered so far.
"The passenger ferry was on its way out of Dhaka when a sand-laden barge hit it from behind, causing it to sink," said police official Selim Sajad.
Six children and 13 women were among the dead, with some of the victims being elderly. A team of 20 divers has begun searching for the sunken ferry in the 15-metre (50-foot) deep water.
"The divers are facing problems since it became dark and now they are not finding any more dead bodies. A salvage vessel is on the way," Hossen said.
Army, fire and coast guard personnel have also been deployed as part of a search and rescue operation, while thousands of people, some of them distraught relatives, massed on the river bank.
"So far we know around 50 to 60 people managed to swim to the shore," said Sajad, adding that the accident happened in calm weather.
Officials said it was possible some unaccounted for passengers had swum to shore and returned home without reporting to the authorities.
Deadly ferry accidents are common in Bangladesh, which is criss-crossed by a network of about 230 rivers that are widely used by millions of people.
It is estimated that more than 3,000 people have lost their lives in ferry sinkings since 1977.
The last major ferry accidents took place in May 2005, when some 110 people died in two separate incidents that happened within days of each other.
In February of the same year, 150 people were killed when a ferry capsized.
The accidents are mostly blamed on profit hungry owners who modify boats to maximise capacity and refuse to allow them to leave port without at least three times the permitted number of passengers.
Crews say the overloading and modifications make the vessels unstable. Such boats, when caught in a storm for example, flip over quickly, trapping people on the lower decks - rather than slowly tilting to one side and sinking like properly built boats, giving people time to escape.
Successive governments in the graft-ridden country have failed to tackle the problem due to their reluctance to take on powerful vested interests.
Despite the dangers, people in the impoverished delta nation have little choice but to continue travelling by boat.
Bangladesh has been under emergency rule since January 2007, when a military backed-government took power promising to clean up the country's notoriously corrupt politics.