SHANGHAI: The court hearing into Shanghai's biggest ever money-laundering bust opened on Friday.

Three Singaporeans and a Fujian native, hired by a Singaporean currency exchange operator Blooming Enterprises (BE), are accused of illegally remitting more than 5 billion yuan ($656 million) between Shanghai and offshore accounts, Shanghai No 1 Intermediate People's Court was told.

One of their major clients was involved in Internet foreign currency margin trading, illegal in China, and allegedly cheated clients out millions.

Loh Foytau, Mok Kwokkee, Lee Keeyong and Chen Peixiang, are charged with operating an illegal business, and face a maximum of 15 years in prison.

All four men claimed they had no idea running a business transferring funds between China and foreign countries, without authorization, was illegal.

Lee, a Singaporean, said that it was legal in Singapore, but conceded a licence was needed.

"I was hired by Loh Foytau in early 2004 and what I did was simply go to banks, and transfer money," Lee, 38 told the court.

"And I had no idea of what those transfers were for."

Lee said that from May 2004 to May 2006 he went to banks almost every day.

"I went there and sent the money, which was transferred to my accounts, to accounts my boss gave to me," he said.

Lee told the court he was handling up to hundreds of thousands of yuan every day.

Investigations found more than 68 accounts in 11 banks were opened for the group's operation.

Loh, 30, the head of the four, said he received orders from Wu Mingguang, the owner of the currency exchange company in Singapore.

The prosecutors did not mention the current situation of Wu Mingguang and his company.

However, a scanned copy of a report on China's tight money laundering rules was found on Loh's computers.

The attorney of Chen Peixiang, 34, argued that there was no clear evidence that could prove the gang was involved in money laundering, or what they were doing was illegal.

Since 2006, China has cracked down on money laundering schemes after several such cases were discovered.

Early this year, Wu Ying, a 26-year-old woman in Yiwu, Zhejiang Province, was found to have been operating and "underground banking" scheme, and allegedly owned assets worth at least 3.8 billion yuan.

She was arrested and is still being investigated