By Agence France-Presse
Five people, including a Chinese national, were arrested during the operation in the capital late Friday, Keo Thea, head of the Phnom Penh Anti-Trafficking unit, told AFP.
"We found 33 surrogate mothers, some have already given birth, some are still pregnant," he said, adding that the women had been offered up to $10,000 to give birth for Chinese clients.
China's easing of its one-child policy two years ago has produced booming demand for fertility clinics, with figures estimating that 90 million women became eligible for another child after the rule was phased out.
But surrogacy is illegal in China, forcing those who can afford it to look for potential options abroad.
Southeast Asia was long a popular international surrogacy destination, with cheap medical costs, a large pool of poor young women and no laws excluding gay couples or single parents.
But in recent years countries in the region have cracked down on the trade, following a series of scandals and criticism that the business exploited poor women.
Cambodian authorities banned the practice in 2016 after prospective parents turned to the impoverished country in the wake of a ban in neighbouring Thailand the previous year.
An Australian nurse jailed for 18 months for running a surrogacy clinic in Cambodia had her sentence upheld in January in a prominent case highlighting the country's role in the trade.
"This is another case of surrogacy despite it being banned," Keo Thea said, adding that the Cambodian women would be sent to the Social Affairs Department pending an investigation while the five suspects will appear before a judge tomorrow.