Australian police Friday said they were investigating a string of hacking attacks against Melbourne-based companies, reportedly linked to recent violence against Indian nationals.

The cyber raids, which have occurred in the past week, are being probed by a specialist taskforce, a spokeswoman said, refusing to confirm media reports that they were linked to the Indian assaults.

"The Victoria Police e-crimes squad is investigating reports of alleged hacking of a number of different business servers hosted in Melbourne," the spokeswoman told AFP.

"The ongoing investigation is in its infancy and it would be inappropriate to comment any further."

The Australian newspaper reported that several Melbourne construction and engineering firms had been attacked in recent days by a hacker called "Ghost Buster".

"Your server data have been compromised ... and have been encrypted," Ghost Buster wrote on one.

"Stop racial attacks against Indian people," the message said, vowing that until the assaults end, Australian servers will be hacked "every day".

Attacks against Indians, including beatings and robberies, have been on the rise in Australia, threatening to damage diplomatic ties and the country's 15.4-billion-US-dollar education export industry.

Media outrage in India has been stoked by the unsolved murder of 21-year-old Punjabi student Nitin Garg in Melbourne last month.

Australian officials had previously downplayed racism as a motive behind the spate of attacks. But Foreign Minister Stephen Smith on Tuesday acknowledged race as a factor and said the violence was "anathema" to modern Australia.

The cyber raids follow one on the public website of the Royal Australian Air Force during the height of attacks last year on Indians.

"Long live India. This is a warning message to the Australian govt," read a message left by hackers in July, according to The Australian.

"Immediately take all measures to stop racist attacks against Indian students or I will pawn all your cyber properties like this one."