Immigration Director-General Khairul Dzaimee Daud said officers raided the building used as the syndicate's call center in Cyberjaya town in central Selangor state on Wednesday after a month of surveillance and caught the alleged scammers in action.
He added that 603 men and 77 women were detained, but about 100 others escaped after charging through a security barricade and attacking officers. He said the detainees, aged between 19 and 35, entered the country using social visit passes and couldn't produce their passports, but are believed to be Chinese nationals.
He said some immigration officials and suspected scammers were injured during scuffles. Local media said online video showed some people jumping from a building ledge onto a tree and sliding down while dozens ran across a road.
Khairul said 8,230 cellphones, 174 laptops and 787 desktop computers were seized.
He said the syndicate has been operating for six months, targeting victims in China with promises of quick returns and using Chinese banks and WeChat mobile payments for their transactions.
All of the Chinese nationals could not produce their passports or travel documents after being arrested, and no representative could produce valid documents on behalf of them, the immigration chief added.
A number of immigration officers required treatment for injuries after scuffles broke out during the bust, and up to 150 Chinese nationals are thought to have escaped from the building.
Malaysian authorities have made similar arrests before to shut down telephone scams targeting victims on the Chinese mainland, but this was believed to be one of the biggest operations in the country.
Those arrested had violated Malaysias immigration laws by entering the country on social visit passes with some overstaying their visa time limits.
On Friday, Chinese Foreign Ministry spokesman Geng Shuang said the Chinese embassy in Malaysia had been briefed about the arrests.
China supports Malaysia in cracking down on such crimes according to the law, and hopes Malaysia will deal with the case with justice, Geng said.
He emphasized that Chinese citizens overseas should follow local laws and avoid taking part in any forms of criminal activities.