The search for victims in the rubble of a collapsed building in southern Cambodia drew to a close Sunday with the final death toll at 36 - the latest tragedy in a string of deadly construction accidents.

Cambodia Prime Minister Hun Sen said 23 people had been pulled alive from the rubble of the seven-storey hotel, which crumpled to the ground in seaside Kep on Friday afternoon.

On Sunday rescuers also managed to free a dog trapped in the debris.

AAP

"This is yet another tragedy," said Hun Sen, who promised families of victims would get $50,000 each in compensation, while those injured would receive $20,000, he said.

He told reporters the contractor responsible for the construction had died in the accident, while the building's owner had been detained.

The rescue effort lasted more 40 hours, mobilizing hundreds of soldiers and labourers using excavators, drills and power saws to clear concrete and cut through metal bars of the pancaked structure.

Cambodia is undergoing a construction boom, with hotels, high-rises and casinos springing up under little regulatory oversight.

The tough and often dangerous labour is undertaken by an estimated 200,000 construction workers, mostly unskilled, reliant on day wages and not protected by union rules, according to the International Labour Organisation.

Last June some 28 people died in the collapse of a building under construction in Sihanoukville, a beach town flush with Chinese investment that.

EPA

Worker advocacy groups point to low safety standards that raise the risk of accidents at construction sites - which often serve as the temporary homes for the labourers and their families.

Worker Ei Kosal told AFP on Saturday that he, his wife and two other women were having a meal on site when the building collapsed.

Their two companions were crushed.

"I did not expect to survive... it's like I have just been reborn," Mr Kosal said from hospital.