At least 12 people have been killed and about 25 are missing following a collision between two boats on a river in the central Bangladeshi district of Munshiganj.

It is the second serious accident involving a ferry over the last year.

The search continues, but chances of finding survivors are slim

The accident happened when a smaller boat was hit by a passenger ferry at the confluence of the Shitalakhya and Dhaleswari Rivers early on Saturday morning.

It is thought the boat was carrying more than 50 passengers when it was hit and sank at a spot about 30 kilometres (20 miles) south of Bangladesh's capital, Dhaka.

It sank quickly and police say that 10 people were killed instantly, but that about 20 passengers managed to swim ashore.

The river was covered with a thick fog at the time of the accident, reports say.

A search operation involving local people and divers has been launched to find the missing passengers.

Police say the chances of finding more survivors are slim as the stricken vessel sank in deep waters in the middle of the river.

Few alternatives

This tragedy is once again likely to raise questions about safety on the numerous boats and ferries that transport large numbers of people across the many rivers of Bangladesh, says the BBC's Dhaka correspondent, Alastair Lawson.

In May, at least 350 people were killed when a ferry sank in bad weather on the River Meghna.

On that occasion, the government was accused of doing too little to enforce safety standards on ferries, many of which are in poor condition and are overcrowded.

There are also complaints that rescuers lack sufficient resources to respond to the tragedy.

The authorities say they are trying to build more roads and bridges to prevent people from using dangerous ferries.

But that will take time in a poor country renowned for its floods and that is criss-crossed by some of the largest rivers in the world, our correspondent says.