PHNOM PENH (Reuters) - Cambodian authorities 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.

The move is part of a regional crackdown as China battles telephone and internet scams that have cost billions of dollars in losses, with fraudsters posing as government officials to target everyone from the elderly to businessmen with legal woes.

Cambodian police said 225 Chinese nationals, 25 of them women, were arrested in Phnom Penh, the capital, on Wednesday. Immigration authorities said another 151 Chinese and three Taiwanese had been arrested on Aug. 2 in the provinces of Siem Reap and Banteay Meanchey.

Those arrested were suspected of using internet voice calls for an extortion scheme, 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,” he told Reuters, without elaborating.

Domestic media published pictures of a police raid showing workers with their hands above their heads in front of tightly packed rows of laptops.

China made no immediate comment on the arrests.

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.

In recent years, Cambodia has deported to China more than 600 Chinese and Taiwanese arrested on suspicion of telecoms scams. In July, Cambodia deported 105 Chinese and Taiwanese suspects to China.

Last month, Indonesia detained more than 150 Chinese nationals accused of a scam that pulled in an estimated $450 million, by tricking victims into paying to make legal cases go away.

Since 2011, Taiwan and mainland China have cooperated in investigating telecoms fraud in Cambodia, Indonesia, the Philippines and elsewhere. Thousands of suspects, many from Taiwan, have been arrested since.

But the arrests and deportations are also a source of friction between Taiwan and Beijing, which accuses Taiwan of harboring criminal gangs behind many of the scams that have targeted victims on the mainland.

Taiwan has also been unhappy that Taiwanese suspects have been deported from countries like Cambodia to China and has accused Phnom Penh of acting at the behest of Beijing.

China has defended the deportations of people from Taiwan to China, saying the criminals should face justice in China, where their victims were.

Some of the suspects will go to China this week when it sends a plane to take them there, immigration official Uk Heisela told Reuters.