Darwin, Jun 28 (IANS): Chief Minister of Australia's Northern Territory (NT) Michael Gunner said the state "is now facing its biggest threat" since the Covid-19 crisis began, adding that its capital city Darwin would enter a lockdown for 48 hours.

The full lockdown was effective from local time 1 p.m. on Sunday at Darwin, Palmerston and Darwin rural areas, following confirmation of four new positive cases linked to a mine, according to the NT government's statement.

According to Australian media, the cases could be linked to the highly infectious Delta strain, reports Xinhua news agency.

The lockdown period means people living in these areas are only permitted to leave home for five reasons, including for medical treatment, essential goods and services, essential work and so on.

Masks must be worn if people leave their place of residence.

"The Northern Territory is now facing its biggest threat since the Covid crisis began. I cannot rule out the lockdown being longer," Gunner said.

The announcement came after Australia's most populous state of New South Wales (NSW) on Saturday extended the ongoing lockdown to more areas as local transmission in the biggest city of Sydney continued to increase.

Jamie Chalker, NT's police commissioner, assured local people that no positive cases were found in remote communities.

Till date, NT has reported 181 coronavirus cases and no deaths.

The country's overall infection tally and death toll currently stood at 30,499 and 910, respectively.