A former Vietnamese refugee shot dead on a Sydney street corner had laundered up to A$1 billion ($830 million) at Australian casinos as he cleaned up cash for criminal syndicates, reports said.

Pete Tan Hoang, an orphan who arrived in Australia as a refugee but went on to become a citizen, was gunned down in a Sydney suburb in September.

"We have certainly considered that he was involved in drug trafficking and moving money through casinos," New South Wales police homicide squad commander Mick Willing told the Australian Broadcasting Corporation, adding this could have led to his death.

Hoang, 36, is thought to have been a key money launderer in Australia, receiving millions in cash from criminal syndicates that he then laundered through gambling.

Although he was banned from some casinos, including The Star in Sydney, others gave him preferential treatment as a high-roller, giving him complimentary flights, luxury accommodation, alcohol and cash payments, the ABC and Fairfax reported.

In 2012, a compliance manager from Melbourne's Crown Casino said in court that Hoang bought gambling chips worth A$75 million between 2000 and 2012 that equalled a gambling turnover of at least A$225 million, the reports said.

The prosecutor at the time suggested the gambling turnover from this could possibly be as high as A$1 billion.

"What's interesting about Mr Hoang's gambling patterns is that they were such big stakes," said Linda Hancock, a social science professor from Deakin University who has researched casinos.

"You know, he's reported as having staked over $100,000 on a hand."

Crown has said it had been assisting law enforcement authorities in relation to Hoang, who was facing charges at the time he was killed.

The Australian Crime Commission said it did not comment on who it might be investigating, but it said on Friday it conservatively estimated that serious and organized crime cost Australia A$15 billion every year.

Recent estimates suggested the level of money laundered in and through Australia was at least A$10 billion a year and this was achieved in a variety of ways, it said.

New South Wales Police organized crime squad commander Scott Cook said the problem was "right across our economy and society".

"Most of that is done through money laundering processes. So it's a significant lifeblood of organized crime," he said.

Cook said criminals saw casinos as places to both flaunt their wealth and places where they can potentially manipulate the processes to launder cash.

"Casinos deal in large quantities of cash. Organized crime has large quantities of cash that they want to launder. So it's a perfect fit in that sense," Cook said.

(China Daily 12/13/2014 page11)