SIHANOUKVILLE: Hopes more survivors may be found under the rubble of a collapsed Cambodian building evaporated Monday as the death toll hit 25, and the prime minister ordered inspections of all construction sites at the beach town which is undergoing a Chinese-bankrolled development boom.

The seven-storey Chinese-owned building folded in on itself before dawn on Saturday as scores of workers slept on the under-construction floors.

Grim processions of stretchers carrying bodies have punctuated the two days since, as workers claw back the twisted metal and concrete debris.

A grim-faced Cambodian premier Hun Sen visited the scene of the collapse in Sihanoukville before daybreak on Monday.

He ordered inspections of all building sites in the town, where condos and hotels are springing up to cash in on the surge in Chinese visitors to its dozens of casinos.

The governor of Preah Sihanouk province, meanwhile, resigned on Monday.

Yun Min accepted he had made a managerial "mistake", according to a post on Hun Sen's Facebook page.

Three Chinese nationals and a Cambodian landowner have been held for questioning over the building collapse.

Residents near the disaster scene said they had long feared tragedy was imminent.

"These buildings are coming up in just a year," said Sock Dara, 45.

"We have been concerned for a long time about the quality of these Chinese buildings."

Authorities on Monday put the death toll at 25.

An AFP reporter saw a partially buried body, covered by a mosquito net, as the debris was cleared by hand, pneumatic drills and diggers.

"We don't expect any more survivors," a soldier who has manned the scene throughout told AFP, requesting anonymity.

- Billion dollar town -

Distraught relatives at a local hospital said around a dozen people were believed to still be entombed in the concertinaed floors of the building.

"I lost my husband and my nephew," said Khim Pov, 47, crying and hugging her daughter as her son -- who was able to crawl from the debris -- received treatment.

"I don't have any hope my husband has survived. The bodies being pulled out have been flattened," she told AFP.

The once-quiet fishing village of Sihanoukville has seen a remarkable Chinese construction boom driven by the need for rooms for tourists flocking from the mainland to its dozens of casinos.

The Chinese embassy in Cambodia, a strategically important ally to Beijing with ports and borders to other Mekong countries, expressed their condolences and backed a "thorough investigation" of the role of the three Chinese nationals and the cause of the accident.

There are an estimated 200,000 construction workers in Cambodia, most unskilled, reliant on day wages and not protected by union rules, according to the International Labour Organization (ILO).

There are also thousands of Chinese workers employed on Beijing-funded projects, fuelling tension with local labourers who envy their better pay and conditions.

Beijing is pouring investment into Cambodia as part of its behemoth Belt and Road initiative, a sweeping trillion-dollar infrastructure programme across Asia, Africa and Europe.

Around $1 billion was invested in the Preah Sihanouk province between 2016 and 2018 alone, and there are around 50 Chinese-owned casinos and dozens of hotel complexes under construction in Sihanoukville. —AFP