Philippine authorities have detained more than 250 people, most of them Chinese, in a raid on a suspected online scam farm in Manila, law enforcement officials said Friday.

Police and other authorities raided the office building late Thursday to find staff with hundreds of phones, computers, and pre-registered international and local SIM cards, the Presidential Anti-Organised Crime Commission said.

"These are red flags of love scamming that victimizes foreign nationals," the commission said in a statement, referring to schemes in which scammers pretend to have romantic feelings for their victims in order to earn their trust and eventually steal their money.

International concern has been growing over similar scam farms in Asia, often staffed by victims of trafficking who were tricked or coerced into promoting bogus crypto investments and other cons.

In July, President Ferdinand Marcos outlawed all forms of offshore gaming operators, including internet gaming licence holders, after the gambling industry was found to be linked to financial scams, kidnapping, prostitution, human trafficking, torture and murder.

Thousands of foreign workers at the outlawed firms were given two months to leave the Philippines.

In the Manila raid on Thursday, 190 Chinese, two Taiwanese and 62 Filipinos were detained at the offices of a company called 3D Analyzer Information Technologies Inc.

The company used to have an internet gaming licence but subsequently told regulators it had "ceased operations", Gilberto Cruz, the executive director of the anti-crime commission, told AFP.

"We're looking for their passports or working visas, but they couldn't show us anything," Cruz added.

The commission will liaise with the Beijing and Taipei missions to help identify and arrange the deportation of the foreigners, the official said.

Meanwhile, Filipinos found to be involved in scamming activities will be charged in court, he added.

Cruz said the commission would also apply to the courts for warrants to search computers found inside the office.