The arrested suspects included both men and women but they declined to answer most questions, said an investigator
Philippine police said they arrested more than 350 people on Thursday over a major telephone scam that swindled people out of millions of dollars in Taiwan and mainland China.
At least 357 suspects, believed to be mostly from Taiwan and China, were arrested after simultaneous raids on 20 houses across Manila, said Senior Superintendent Ranier Idio, deputy chief of an anti-organised crime task force.
"This is a big syndicate. They go for the millions (of dollars)," he told reporters.
The gang would pose as police and government prosecutors, telling their victims by telephone that they had legal problems and they would have to transfer money to a certain account to settle the matter, said Idio.
He said the group would carefully check their intended victims' background to make sure they could pay up before they struck.
They chose to operate in the Philippines to avoid Chinese police and because of the country's proximity to China and Taiwan, according to Idio.
Police said many of their victims were elderly retirees.
Numerous computers and telephone systems were recovered in the raid, Idio added.
The arrested suspects included both men and women but it was difficult to get further details out of them as they declined to answer most questions, said Senior Inspector Robert Reyes, one of the investigators.
"Mostly, they are not cooperative. We don't know if they can't speak English or if they just don't want to talk," he told AFP.
Envoys from mainland China and Taiwan were at the police centre, determining where the suspects had originated from, police said.
The syndicate, operating in cells, would bring their gang members to the Philippines in small groups and put them up in rented houses in upscale neighbourhoods to avoid raising suspicion, police said.
Two Filipinos who facilitated the entry of the foreigners were also arrested.
Reyes said police suspected the group was linked to 78 Taiwanese suspects who were arrested in the southern Philippines in April, also for using telephone systems to obtain money from mainland China and Taiwan.
The Taiwanese were later deported to face charges at home, authorities said.
The latest suspects could be charged with a law penalising the use of telecom systems to commit fraud, Reyes said. If convicted, they could face six to 20 years in jail.