At least 339 people died in Phnom Penh in a stampede at the end of the annual Water Festival.
The numbers of dead continued to rise as the night wore on. At one point, there were more than 30 bodies on the bridge in Phnom Penh; a Cambodian Red Cross worker said shortly afterward that at least another 70 had died.
After midnight Cambodian Prime Minister Hun Sen went on television to tell a shocked nation that 339 people had died on the pedestrian bridge linking Diamond Island in the Tonle Sap river with the mainland, and about 329 had been injured.
It was, he said, the worst loss of life since the overthrow of the Khmer Rouge in 1979.
Most of the victims were young people in their teens and twenties, some of the estimated 2 million who had flocked to Phnom Penh for the annual Water Festival, which marks the end of the rainy season.
Most suffocated on the bridge, which thousands of people were using to leave Diamond Island. Others drowned after jumping from the bridge into the water. Some reportedly were electrocuted because of wires in the water
Ly Vuthy was selling drinks near the bridge on Diamond Island at the time. She says the bridge was packed with people trying to get back to the mainland, and several people fainted.
Others then panicked, and the crowd surged back and forth, unable to get off the bridge.
She says people felt trapped, and many jumped into the river below.
Sem Pagnaseth, a vendor on the mainland side, said thousands of people were crammed on to the 100-meter long bridge trying to leave.
He said crowd barriers on the mainland side were set up to stop people spilling on to the road. But the volume of people leaving meant some could not move away quickly, and that caused a jam on the bridge.
He says only a few police were working on crowd control at the bridge before the incident, but once the stampede began, the police acted quickly to pull as many people out as possible. Their quick action, he says, certainly saved many lives.
The dead and injured were ferried to hospitals in ambulances, pick-up trucks and private cars.
Two hours after it happened, the bridge was littered with hundreds of shoes, articles of clothing and water bottles. Boats were scouring the waters of the river below for more bodies.
It was a tragic end to what should have been a festive visit to the capital. Over the coming week hundreds of families across Cambodia will be holding funeral services for their loved ones.
Early Tuesday Hun Sen said the government would establish a committee to work out what had gone wrong.