Videos posted on social media on Thursday showed people falling from a roof after they were trapped by the fire at the Grand Diamond City casino and hotel in the border town of Poipet. Many of those inside, both customers and staff, were from neighbouring Thailand.
In a video posted by Cambodia's firefighting agency, onlookers could be heard shouting pleas to rescue people trapped on the roof of the hotel complex, which is more than a dozen stories tall at its highest point. The video showed at least one man falling as the flames reached the roof.
"Oh, please help rescue them. Pump water ... pump water," shouted the onlookers.
The Department of Fire Prevention, Extinguishing and Rescue posted that calls for help were heard from the 13th, 14th and 15th floors at 4am and hands were seen waving from windows as well as a mobile phone's flashlight signalling from inside the complex.
"The fire was massive, and was inside the casino, so it was difficult for our water cannons to reach it," observed a firefighter on the video posted online by the fire department. He said that was the reason the fire continued burning for such a long time.
The blaze, which started around midnight Wednesday, was finally put out at 2pm on Thursday, said Sek Sokhom, head of Banteay Meanchey's information department. He said a local Buddhist temple was being prepared to receive the dead.
The province's deputy governor, Ngor Meng Chroun, told Cambodia's Bayon Radio the death toll had reached 16, with about 50 other people injured. The number of deaths appeared likely to rise, as more bodies of those trapped inside were discovered and critically hurt people succumbed to their injuries.
Banteay Meanchey police chief Sithi Loh said 360 emergency personnel and 11 firetrucks had been sent to the scene of the fire, whose cause was not yet known. The casino employed about 400 workers.
"Right now, we are trying to bring the dead bodies from the building down," said Montri Khaosa-ard, a staff member of Thailand Ruamkatanyu Foundation, a social welfare organisation that sends volunteers to the sites of emergencies.
"I don't think there will be any survivors because of very thick smoke. Even we all (the rescue staff) have to wear proper gear when we go inside the building, otherwise we cannot breathe at all."
Thai and Cambodia rescue teams worked side by side in Thursday's search of the badly burned premises.
Thailand's public television network, Thai PBS, reported that 50 Thais, both staff and customers, had been trapped inside the casino complex. It reported that Cambodian authorities requested help to deal with the fire from Thailand, which sent five firetrucks and 10 rescue vans.
Poipet in western Cambodia is opposite the city of Aranyaprathet in more affluent Thailand, and there is busy cross-border trade and tourism.
Thai PBS cited reports that Aranyaprathet Hospital's emergency ward was full and other victims had to be sent to other hospitals.
Casinos are illegal in Thailand, but neighbouring countries such as Myanmar, Cambodia and Laos host the lucrative industry. Cambodia has an especially active casino industry because the Southeast Asian country is also a popular tourist destination with convenient international connections.
The Grand Diamond City casino is just a few metres from the border checkpoint with Thailand and popular with customers who make the four-hour drive from the Thai capital, Bangkok.
