Chinese police have shut down 1,664 mafia-style groups involved in fraudulent lending and seized 16,349 suspects since a national campaign against organized crime was launched in early 2018, the Ministry of Public Security said Tuesday.

Since early 2018, police have cracked 21,624 fraud and extortion cases and sealed assets worth 3.53 billion yuan (527 million U.S. dollars) related to such crimes, said Zeng Haiyan with the ministry at a press conference.

Under the guise of private lending, the criminal rings deceived victims into signing false contracts, tried to put them in debt by forging evidence to make them breach their contracts and illegally possessed the victims' property through violent measures such as illegal detention and extortion, said the ministry.

Investigations found that some organized crime groups had used online lending platforms to commit fraud, bringing harm to a large number of people.

In one case, police in the city of Wenling, Zhejiang Province, bust a syndicate and seized 263 suspects in June 2018. The ring was found to have given out loans to more than 90,000 people through online platforms between August 2017 and May 2018, illegally gaining more than 100 million yuan.

In another case, 129 suspects from a fraudulent lending ring targeting college students were arrested by police in the city of Anyang, Henan Province. The group's members had harassed and threatened students who were unable to repay the loans by sending nude photos or insulting text messages to them or their family members, teachers and classmates.