Australia reported five new swine flu-related deaths, taking the country's total to 18.

Four of the deaths, which all occurred in recent days, were in the state of Victoria while the fifth was in New South Wales, officials said.

"All four had underlying health conditions which made them more susceptible to illness," Victoria's deputy chief health officer Rosemary Lester said.

Lester added that a total of 11 people with the A(H1N1) virus had died in Victoria, stressing that the disease was mild in most cases.

"However, as we have consistently stated, influenza can be severe for people with chronic medical conditions," she said.

In neighbouring New South Wales, a 27-year-old man with pre-existing medical problems died on Saturday in a hospital in Newcastle, north of Sydney.

Swine flu has hit 6,364 people in Australia, the Asia-Pacific region's worst-affected country, including 1,876 in Victoria and 1,532 in New South Wales.

The virus has not been confirmed as the cause of any of the deaths, although one case involving a three-year-old boy from Victoria is under investigation.