In a major crackdown, the police have solved 574 "unfreezing national assets" fraud cases involving 12.95 billion yuan ($1.82 billion), an official at the Ministry of Public Security said on Friday.

The special campaign launched by the ministry in February led to the capture of 4,385 suspects and dismantling of 247 criminal organizations involved in the crime, Chen Shiqu, deputy head of the ministry's criminal investigation department told a news conference.

The ministry has kept up efforts to combat the decades-old scheme where fraudsters falsely claim they have access to national assets overseas that are frozen, and that people paying "initiation fees" to unfreeze them will gain a huge sum of reward.

In recent years, such fraud schemes have taken on new forms, with fraudsters forging government documents, certificates and stamps, and luring a large number of people online into investing in fake government projects, Chen said.

The criminal organizations would also develop special apps to recruit new members, while they themselves and their financiers hide overseas, Chen added. "These tactics are becoming increasingly similar to those used in telecommunications and cyber scams."

During this year's campaign, the ministry has supervised the investigation of 26 key cases.

Among typical cases revealed on Friday was one cracked by the police of Jilin city, Jilin province, this year, where suspects fabricated a "welfare housing policy", developed a fake app and hoaxed victims into buying "housing tickets".

The city's police have captured more than 400 suspects, including seven who had fled abroad and been referred to the Interpol Red Notice list, and seized and frozen more than 30 million yuan, according to Liu Hong, deputy head of the city's public security bureau.

The ministry also revealed 50 fraudulent schemes and apps to the public on Friday.

Chen said that the ministry will continue to crack down harshly on the fraud, and make it a key task for public security authorities across the country to target the crime.

The authorities will get to the bottom of the organizational structure of the criminal groups, speed up efforts to bring to justice their financiers, organizers and agents at top levels, he said.

They will also investigate thoroughly apps developed for conducting the fraud, as well as money laundering and transfers related to the cases, he said.