AUSTRALIAN police suspect the nephew of Cambodia's Prime Minister is involved in a heroin trafficking and money laundering syndicate targeting Australia.

But a plan to arrest and question Hun To in Melbourne was thwarted because his application for a visa was denied by the Australian embassy in Phnom Penh, with one official citing the need to avoid a diplomatic incident. The targeting of Mr Hun To by an Australian Crime Commission inquiry that ran between 2002 and 2004 is one of several incidents that suggest strong and continuing links between Australian crime figures and Cambodia.

Cambodian Prime Minister Hun Sen ... Australian police suspect his nephew of being involved in a crime syndicate targeting Australia. Credit:Bloomberg

The Herald can also reveal that Sydney crime figures have been investing millions of dollars in suspected drug funds in big businesses in Cambodia, including those tied to influential government and business identities.

The revelations came after the Herald on Saturday reported that Australian officials had uncovered a global crime syndicate importing more than $1 billion worth of drugs into Australia annually and with connections to government and policing officials in Asia.