Winny Wang/ Shanghai Daily news

A Shanghai court this morning began hearing China's biggest money laundering racket case involving five billion yuan (US$633 million), Shanghai Evening Post reported.

The Singaporean defendant said he and three accomplices were exchanging foreign currencies in rented apartments in Shanghai and Suzhou.

They received foreign currencies from the boss of a Singaporean money-exchange company and deposited the money into local banks twice a day.

The group laundered more than five billion yuan in 68 banking accounts from January 2004 to April 2006 and were arrested last year, the report said.

The case first surfaced in a Pudong Branch of the Bank of Communications. Employees there reported to the central bank's anti-money laundering bureau that a man had been making money transfers every day from the first quarter of last year.

Banking employees asked him to apply for a VIP card which would give him preferential treatment as he seemed to be a really big client but he refused.

"It was really strange that he kept making money transfers at different windows of the bank, and showed no dismay at the long queues in front of him," an official with the branch said.

A later investigation by the bureau uncovered that he wasn't working alone, and his accomplice was working in other banks in Shanghai.

The group were later arrested and accused of operating an underground bank in the city, making large money transfers and providing foreign exchange and other banking services between Singapore and China.