A stampede in the Cambodian capital has left more than 340 people dead and hundreds injured after panic erupted at a water festival that had attracted millions of revellers.
Dozens of ambulances with their sirens blaring raced to the scene of the incident, which occurred late Monday on a narrow bridge to an island in Phnom Penh where festivities were being held to mark the end of the annual event.
Prime Minister Hun Sen described it as Cambodia's darkest hour since the Khmer Rouge, whose 1975-1979 rule left up to a quarter of the population dead.
"This is the biggest tragedy since the Pol Pot regime," Hun Sen said in a live television broadcast, referring to the Khmer Rouge's late leader.
He said Cambodia would hold a national day of mourning on Thursday.
"I would like to share my condolences with my compatriots and the family members of the victims," he said.
The prime minister said arrangements would be made for the bodies of out-of-town visitors to be sent home.
The stampede left at least 345 people dead and 410 injured, a government spokesman told AFP.
"Most of the deaths were as a result of suffocation and internal injuries," Khieu Kanharith said.
It was not immediately clear what triggered the stampede, but he said a rumour had spread among the revellers that the bridge was unstable.
"So panic started. It was too crowded and they had nowhere to run," he said.
Witnesses reported people pushing and shoving in the crowd.
"We were crossing the bridge to Diamond Island when people started pushing from the other side. There was lots of screaming and panic," 23-year-old Kruon Hay told AFP at the scene.
"People started running and were falling over each other. I fell too. I only survived because other people pulled me up. Many people jumped in the water," he said.
Sunglasses and flip-flops were left scattered on the ground among lifeless bodies of people.
Police were seen carrying away some of the victims while others were laid in a row on the ground. Many of the dead appeared to be young Cambodians.
"This is the biggest tragedy we have ever seen," said Sok Sambath, governor of the capital's Daun Penh district.
Dozens of people gathered outside the city's Calmette hospital, where at least 105 people were confirmed dead, according to a police officer.
More bodies were taken to other hospitals across the city, he said.
Many festival-goers were left in tears after the tragic end to the three days of boat races, concerts and fireworks.
The annual festival, one of Cambodia's largest and most exuberant, marks the reversal of the flow between the Tonle Sap and Mekong rivers.
It is also seen as a way of giving thanks to the river for providing the country with fertile land and abundant fish.
The event - which saw hundreds of brightly coloured boats take part in races on the Tonle Sap river - is popular with tourists but there were no immediate reports that foreigners were among the victims.
The last time the festival was marred by tragedy was in 2007 when five Singaporeans were killed after their dragon boat, carrying 22 men, capsized at the end of their race.
Accidents are common during the races, which involve long, thin boats crewed by as many as 70 rowers, which compete against each other in the sometimes choppy waters in front of Phnom Penh's royal palace.
AFP/de
