SYDNEY - Australia's mining boom may be fuelling an alarming rise in HIV infections among cashed-up heterosexual outback miners and businessmen in resource-rich states who holiday in Asia, say researchers.

Rates of HIV infections in Australia have increased by almost 50 percent in the past eight years, according to a new national HIV-AIDS report released on Wednesday.

In the year to December 2007, Australia had 27,331 cases of HIV infection and 10,230 cases of AIDS, said the report by the National Centre in HIV Epidemiology and Clinical Research.

"The annual number of new HIV diagnoses in Australia has steadily increased over the past eight years, from 718 cases in 1999 to 1,051 in 2007," it said.

Homosexual men still account for most new infections, but a large number of new infections are amongst heterosexual men in the country's mining rich states of Western Australia and Queensland.

Many miners work fly-in, fly-out shifts consisting of several weeks straight of work followed by a few weeks off and researchers say some are visiting Asia for their downtime.

"A small but significant number (of new infections) are among heterosexual men from the richest resource states, who are clearly taking holidays in Asia and having unprotected sex," said Don Baxter, executive director of the Australian Federation of AIDS.

Baxter said Western Australia men most likely visit Southeast Asian countries, with the state capital Perth about five hours flying time from Asia, while those in Queensland visit neighbouring Papua New Guinea, which experts say is on the verge of an African-style HIV-AIDS epidemic.

"Among heterosexual males in Western Australia there has been a 68 percent increase over the last three years. That's about the same number of heterosexual men as gay men in Western Australia to be infected in 2007," said Baxter.

Baxter said the Western Australia state government and AIDS council was working with mining companies to implement safe sex education programmes for miners.

Health authorities said on Wednesday that a cluster of men in the tropical city of Cairns in Queensland state had contracted HIV after having unprotected sex with women in Papua New Guinea, a short flight north of Queensland.

The Cairns Sexual Health Service said six men, all businessmen aged between 47 and 66, tested HIV positive in the past 10 months.

"This small cluster could just be the beginning of a very large outbreak," Dr Darren Russell, director of the Cairns Sexual Health Service, told local media.

"It indicates the HIV epidemic in PNG is becoming more generalised which puts these men at greater risk, and in that climate the numbers will only rise."

Australia's AIDS federation called on the government to increase funding for AIDS prevention programmes to stem the rising rate of infections.

Australia's most populous state New South Wales, home to Sydney's largest homosexual population, recorded little change in infection rates in the past decade because it had maintained funding for safe sex programmes, said Baxter.

In contrast, infection rates soared in states that reduced funding, with the southern state of Victoria experiencing a 131 percent increase and Queensland a 55 percent rise.

"We have pretty clear evidence that investment in the programmes at least stabilises the rate of HIV infections," said Baxter.