Beijing, Nov 20 (IANS): Police in China's Zhejiang province have busted the country's largest underground banking case, which involved transactions totalling to 410 billion yuan ($64 billion), a media report said on Friday.

At least 100 suspects from eight gangs have been detained since the investigation was launched in September 2014, China Daily reported.

Police said the gangs were united by a ringleader, Zhao, who operated dozens of fake companies in Hong Kong. The companies were involved in foreign exchange transactions and money laundering.

In December 2014, arrest warrants were issued for 56 suspects and more than 3,000 bank accounts were frozen. It took almost a year for police to sort through the over 1.3 million suspicious transactions.

China has faced an "increasingly arduous and complicated" problem with illegal financial institutions often used for laundering money obtained from corruption, online gambling and fraud, according to the public security ministry.

Police have shut down 37 such banks since August.