At least 347 people were killed and 394 others injured in a stampede on Monday night as millions of Cambodians celebrated the last day of the three-day annual Water Festival in the capital Phnom Penh.
"This is the biggest death toll since Pol Pot regime and even flood has never inflicted such a high death toll," Hun Sen said. But he added that "Urgent investigation showed that it has nothing to do with terrorism."
"Taking this opportunity, I would like to express my condolence to all victims and their relatives," Hun Sen said.
The prime minister announced Nov. 25 as the national mourning day to commemorate those people killed in the stampede.
Meanwhile, he urged the doctors to do their best to save the injured people and ordered investigation into the cause.
Deputy Prime Minister Sok An said a national level committee was established to investigate the horrific stampede.
Sok An said the committee divided into three sub-committees: the forensic examination sub-committee led by the Health Minister Mam Bun Heng, the corpse and injured people settlement sub-committee led by the Minister of Social Affairs Ith Samheng, and the investigation sub-committee led by Prum Sokha, secretary of state for the Interior Ministry.
"The committee will deal with all work relevant to the accident, " he said.
The accident took place on a bridge that connects the city with the Diamond Island which has became the center of celebrations. Some of the panicky people tried to flee over the bridge and crushed underfoot while a number of them fell over the bridge into the water.
The injured were rushed to the nearby hospitals, and many were said to have lost consciousness. Ambulance sirens were heard in many parts of Phnom Penh soon after the accident. Some of the hospitals in the capital were filled to capacity with bodies and patients.
Sar Kheng, deputy prime minister and minister of interior, has rushed to the scene.
Cambodia's Water Festival from Nov. 20 to 22 is the largest annual festival in the Southeast Asian nation, around two million Cambodians, especially those from rural areas converged to the city to enjoy the regatta.