A fifth poultry farm near Melbourne has been infected with a highly pathogenic H7 strain of avian influenza, Reuters reported, citing the government of Australia's Victoria state on Wednesday.

The farm is within a restricted zone near three others where the H7N3 flu had already spread in recent weeks, and authorities said the latest detection was not unexpected.

Another farm in Victoria has at the same time hosted an outbreak of a different H7N9 strain of the virus. Neither strain is the same as the H5N1 type that has spread globally through bird and mammal populations and even into humans.

"We are responding to the detection of avian influenza at 5 Victorian poultry farms," the Victoria agriculture department said in a statement.

"All properties have been placed in quarantine and all poultry will be safely disposed of. The sites will be cleaned and cleared of the infection," it added.

More than half a million egg-laying birds have been or will be killed due to the outbreaks, which began last month, but this is a small fraction of the country's flock and industry has sought to reassure consumers about the risk to food supplies.

"It's deflating to see new sites emerge which is terrible for the farms involved and for the welfare of the birds but comfort can be taken that it is within a defined region," Rowan McMonnies, managing director of trade group Australian Eggs, said in a statement this week.

"If this can be maintained the impact on egg supply should remain limited," he said.

Before the latest cases, Australia has suffered nine outbreaks of highly pathogenic avian influenza since 1976, all of which were contained and eradicated, according to the state government. The virus is spread from wild birds.

Officials say there is no risk to the public from eating eggs and poultry meat.