The public security authorities in China have cracked 574 "unfreezing national assets" fraud cases involving 12.95 billion yuan ($1.82 billion) in a campaign aimed to end such fraud, an official of the Ministry of Public Security said at a news conference on Friday.

The campaign was launched by the ministry in February with the capture of more than 4,000 suspects and the disruption of 247 criminal organizations, said Chen Shiqu, deputy head of the ministry's criminal investigation department.

"Unfreezing national assets" is a decades-old guise that fraudsters use to swindle others of their money. They falsely claim they have access to national assets overseas that are frozen, and people who pay "initiation fees" to unfreeze them will gain a huge sum of reward.

In recent years, such fraud schemes have taken on a new form, with fraudsters cheating a large number of people online by making up fake national projects and forging government documents, certificates and stamps, Chen said.

During this year's campaign, the ministry has supervised the investigation of 26 key cases, obtained clear information about the structure of related criminal organizations, their financiers, organizers and key members, and cracked down on the apps developed by the fraudsters, as well as their transfer and laundering of money, Chen said.