BEIJING - Police in China's Jiangxi and Guangdong provinces and Macao Special Administrative Region have seized foreign exchange worth 3 billion yuan ($420 million) involved in illegal transactions in recent joint operations, the Ministry of Public Security (MPS) said on Tuesday.

In two joint operations, 252 suspects were captured for illegally exchanging currencies and related unlawful acts, with 57 of them repatriated to the mainland by Macao police.

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An increasing number of individuals have conducted illegal trading in currencies in Macao in recent years, resulting in other crimes, such as fraud, robbery and human smuggling, posing a threat to public security and people's safety in the region, according to the MPS.

Coordinated crackdowns launched by police from the mainland and Macao uncovered 19 criminal gangs in Macao, Nanchang of Jiangxi, and Zhuhai of Guangdong, with over 300 individuals involved.

Taking orders from the gang leaders, the members performed various tasks, including withdrawing cash from banks, making contacts with illegal banks, and soliciting clients near casinos and hotels in Macao.

The gangs were busted in joint operations under the direction of the MPS.