The Delta COVID-19 virus strain was discovered for the first time among illnesses in the newest virus outbreak in Australia's Victoria state capital, Melbourne, on Friday, according to state authorities.

"The Delta variant is now well-known in India and is becoming more common in the United Kingdom. It's a variation of serious concern" Brett Sutton, Victoria's Chief Health Officer, told reporters in Melbourne.

According to Sutton, no sequenced COVID-19 infection cases from hotel quarantine or elsewhere in Australia have been related to the novel variation.

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

"It's concerning that it's not linked to other cases," Sutton said, "but we're tracking down all those primary-case contacts... and investigating where it might have been acquired."

After more than three months of no cases, Victoria, Australia's second-most populous state, is struggling to manage its newest outbreak - 65 cases since May 24 - by imposing stringent restrictions on people's travel and closing down huge areas of its economy. All of the illnesses have been linked by the government to a single passenger who was released from quarantine after testing negative.

Melbourne is already in its second week under heavy lockdown, which has been extended for another week until June 10, however certain restrictions have been lifted in other parts of the state as of Thursday night.

Although new cases have remained in the single digits for eight days in a straight, authorities blamed the extension of stringent curbs in Melbourne on the Kappa variety, which was initially found in India and described as a highly infectious strain.

On Friday, four additional locally acquired cases were reported, compared to three the day before.

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

As of Friday, more than 4.5 million vaccination shots have been provided in the country, which has a population of around 20 million adults, according to the figures.