PHNOM PENH (Reuters) – Authorities in Cambodia have arrested nearly 400 Chinese and Taiwanese nationals this month on suspicion of operating a telecoms scam to defraud victims in China, police said on Thursday.

China has been battling telecoms fraud that has cost billions of dollars in financial losses, say authorities in Beijing who accuse Taiwan of harboring criminal gangs behind many of the scams.

Cambodia is one of China’s closest allies in Southeast Asia and does not recognize the government of Taiwan, which Beijing considers a wayward province.

Cambodia, one of China’s staunchest allies in Southeast Asia, has deported more than 600 Chinese and Taiwanese nationals in recent years in a crackdown on internet and telecoms scams orchestrated from the Southeast Asian nation.

Police in the Cambodian capital of Phnom Penh on Wednesday arrested 225 Chinese nationals, 25 women among them, who are suspected of running an extortion scheme using internet voice call technology, said Thou Saroeun, deputy director of the anti-terrorism police department.

“We are processing the case and we don’t know yet when this will move to deportation,” Thou Saroeun told Reuters.

On Aug. 2, police arrested 151 Chinese and three Taiwanese nationals in the provinces of Siem Reap and Banteay Meanchey, Uk Heisela, the investigations chief of the immigration department, told Reuters.

The suspects await deportation to China and some will be sent back this week, Uk Heisela said.

“I don’t know when exactly, that depends on when China sends a plane,” he said.

Authorities in Taiwan have accused Cambodia of acting at China’s behest.

Last month, Cambodia deported 105 Chinese and Taiwanese suspects to China, prompting a protest from the self-ruled island to Phnom Penh.

China has defended the deportations of people from Taiwan to China from places like Cambodia by saying the victims were all in China and so the criminals should face justice in China.