The driver lost control of the vehicle, which was overladen with about 50 boys aged between 10 and 15, at Mirershorai, 200 kilometres (125 miles) from the southeastern port city of Chittagong.

"We can confirm the death of 31 children. The dead bodies are now in clinics," district police chief S.A. Morshed told AFP by telephone. "We will have a mass funeral later this evening."

District official Sayeed Kutub told AFP that many victims -- mostly from local Abu Torab Primary School -- had drowned after being stuck under the truck when it turned over into the ditch by the side of the road.

"They were trapped under the sunken truck. It took us some time to turn it over. As a result, most died because of drowning in water. Six children seriously injured have been admitted in clinics," he said.

He added that the toll might increase because some badly injured children had been taken by their parents to nearby health centres before being counted by rescuers.

The boys were returning from a trip to support a team playing in a local football tournament in Mirershorai.

"They hired the truck to travel home quickly. They were enjoying the ride and were celebrating because their team has won the tournament," said Foyez Ahmed, Chittagong district administrator.

Local police initially put the death toll at about 40, but later said they were still counting the toll.

"It was a tragic scene. As we are pulling one body after another, parents and relatives could not control their emotions," Rezaul Karim, a local police officer, told AFP. "Some intervened, making the rescue operation difficult."

Army and Navy rescue teams were brought to dive into the deep road-side ditch.

M. Fokhruizzaman, a doctor at the Chittagong Medical College Hospital, said at least 12 children were admitted to the government facility with serious injuries.

Road accidents are common in Bangladesh and kill thousands of people each year. Shoddy highways, poorly maintained vehicles and drivers' disregard for road safety are blamed for most fatalities.

A recent study by the Dhaka-based Accident Research Center says that more than 12,000 people die in road accidents in Bangladesh every year, making the country's highways among the deadliest in the world.

The country's president Zillur Rahman and Prime Minister Sheikh Hasina expressed their sorrow at the "tragic" deaths. Hasina ordered a quick rescue operation and proper treatment of the injured children.