Australia's Victoria state authorities said on Friday genomic sequencing has detected for the first time the Delta COVID-19 virus variant among infections in the latest virus outbreak in the state capital, Melbourne.

"That variant is the Delta variant, it is now infamous in India and increasingly found in the UK. It is a variant of significant concern," Victoria Chief Health Officer Brett Sutton told reporters in Melbourne.

Sutton said the new variant had not been linked to any sequenced COVID-19 infection cases across Australia from hotel quarantine or elsewhere.

So far, two Victoria cases have the so-called 'Delta' variant of concern. The delta variant, first detected in India and likely the strain that caused the latest devastating wave of COVID-19 in the country, has been officially found in at least 62 countries and regions, according to the latest World Health Organization (WHO) weekly epidemiological report.

"It is a concern that it is not linked to other cases, but we are chasing down all those primary-case contacts ... and looking into where it might have been acquired," Sutton said.

Victoria, Australia's second-most populous state, is battling to contain its latest outbreak - 65 cases since May 24 - after more than three months of no cases, placing tough restrictions on the movement of people and shutting down large parts of its economy. The government has linked all the cases to a single traveler released from quarantine after testing negative.

Melbourne is into the second week of hard lockdown after it was extended for another week until June 10, but some curbs elsewhere were eased in the state from Thursday night.

Authorities blamed the extension of tough curbs in Melbourne on the Kappa variant, first detected in India, which they described as a highly infectious strain, although new cases have remained in single digits for eight days in a row.

Four new locally acquired cases were reported on Friday, versus three a day earlier.

Australia has confirmed 30,141 COVID-19 cases and 910 deaths, according to the latest data from Johns Hopkins University. 

More than 4.5 million vaccine doses have been administered as of Friday in the country, which has an adult population of about 20 million, the data said.

(With input from Reuters)