Cambodia sent home on Thursday 74 Chinese nationals wanted in China on suspicion of extorting money from people there over the internet and by telephone, Cambodian police said.
A team of Chinese police arrived in Cambodia's capital of Phnom Penh on a China Southern Airline flight to pick up the suspects who had been detained in Cambodia.
"They established places to commit crime by extorting money from people over the phone," Uk Heisela, the head of the Cambodian police investigation, told reporters.
"They used Cambodia as the location to extort money from people in China."
The 74 suspects had been arrested in Phnom Penh and Kampot province, he said, adding that it was the first such expulsion this year.
Reporters did not get access to the 74 before they were put on the plane and flown home and it was not clear if any of them had lawyers.
The deportation is the latest by Cambodia at Beijing's behest. Cambodia is one of China's closest allies in Southeast Asia.
In 2009, Cambodia sent home 20 ethnic minority Uighurs, from China's troubled far western region of Xinjiang, despite objections from the UN refugee agency and rights groups, which said they feared for the safety of the Uighurs if sent back.
Last year, Cambodia deported 13 Taiwanese nationals wanted on fraud charges to mainland China despite vehement opposition from Taipei which has accused Beijing of "abducting" its citizens from countries that do not recognise the island's government - such as Cambodia.
Uk Heisela said more than 500 fraud suspects had been deported to China over recent years.