Frantic relatives scoured makeshift morgues in the Cambodian capital on Tuesday after nearly 380 revelers perished in a huge stampede on an overcrowded bridge, turning a water festival into tragedy.
Survivors recounted scenes of panic and fear on the narrow bridge as people were trampled underfoot by the surging crowds on Monday, with some reportedly falling or jumping into the river below or grabbing on to electricity cables.
Prime Minister Hun Sen described the disaster as Cambodia's worst tragedy since the Khmer Rouge's 1975-1979 reign of terror, which left up to a quarter of the population dead. He declared a national day of mourning on Thursday.
The United States offered Cambodia "deep condolences for the tragic loss of life".
At least 378 people were killed in the crush and some 750 were injured, government spokesman Phay Siphan told AFP.
"The number is still going up," he said.
Exuberant festival-goers had been crossing the bridge to reach an island hosting concerts, food stalls and ice sculptures before the crowd turned to a desperate crush of human bodies.
It was not immediately clear what had triggered the disaster, but another government spokesman said a rumor had spread among revelers celebrating one of Cambodia's biggest festivals that the bridge was unstable.
"So panic started. It was too crowded and they had nowhere to run," Khieu Kanharith said.
Many of the deaths were caused by suffocation and internal injuries, he said, adding that about two-thirds of the dead were women.
At the scene of the tragedy, the bridge to Diamond Island was littered with sunglasses and flip-flops and still decked with lights from the huge annual water festival that drew millions into the streets on Monday night.
"There were so many people and they tried to push me and some people stepped on me. I saw a few jump off the bridge," Meourn Piseth told AFP.
"I felt like I was going to die, I couldn't breathe," said the 15-year-old as he received treatment for his badly bruised legs at Preah Ketomealea hospital.
Many witnesses reported seeing people jump or fall from the crossing into the river below.
"We are doing a search around the bridge in case there are bodies in the water," the government spokesman said.
Several hundred worried relatives gathered outside the city's Calmette Hospital trying to identify missing loved ones.
Rows of bodies were laid out under a white tent erected over the hospital car park and people were straining to catch a glimpse of the dead.
Policemen photographed and numbered the victims, while all around people made frantic phone calls describing the outfits of the deceased.
Their uncovered faces showed many had sustained bloody bruises during the stampede.
One woman said she recognized her 16-year-old niece in the makeshift morgue.
"I heard she was killed last night, so I came here and I saw her body," Som Khov, 51, told AFP. "I heard she died from an electric shock."
Some witnesses reported that people had been grabbing electric cables on the bridge, but a doctor at the hospital played down suggestions that electrocution was the cause of some of the deaths.
"It looks like they died from a lack of oxygen," said the doctor, who did not want to be named.
After Hun Sen promised that the government would arrange for the bodies of out-of-town visitors to be sent home, 13 military trucks began taking away corpses from Calmette Hospital.
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, marks the reversal of the flow between the Tonle Sap and Mekong rivers.
The event -- which saw hundreds of brightly coloured boats take part in races on the Tonle Sap -- is popular with tourists but there was no confirmation that any 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.