Images published by the Australian Broadcasting Corp. on Thursday showed police flagging down cars in suburban streets after 36 suburbs in Melbourne in Victoria state went into lockdown following a spike in new infections there. The state reported 77 new cases on Thursday, up slightly from the previous day and in line with two weeks of double-digit daily increases.

"I'm obviously concerned about the outbreak, and I'm pleased that the premier has taken the action he's taken by putting in place the lockdown for the outbreak in those suburbs," Prime Minister Scott Morrison said in a televised news conference, referring to the Victorian state government.

"We have seen some leveling [in new cases] although they remain at elevated levels and that is of concern and that means as the lockdown now is in place, we would hope to see those numbers fall again."

Australia has fared better than many countries in the pandemic, with around 8,000 cases and 104 deaths. However, the recent jump in Victoria has stoked fears of a second wave of COVID-19, echoing concerns expressed in other countries.

Most states have said they will reopen their internal borders except to Victoria. Neighboring New South Wales, the most populous state, has kept its border open except to people arriving from the targeted Victorian suburbs.

"Though these restrictions are in place in those restricted postcodes, there's an obligation on all of us to consider how we minimize our interactions with other people," Victorian chief health officer Brett Sutton told reporters.

"All of us across Victoria have to really consider whether we need to see people in other settings, other households, including family members and friends."

On the other side of the country, remote Northern Territory reported its first infection in two months after a traveler who had entered the country via Melbourne and completed the mandatory two-week quarantine showed symptoms after returning to his home territory.

"People will be anxious hearing this news ... but we have measures in place to protect our community [and] these measures have been followed," Northern Territory Health Minister Natasha Fyles told reporters.

The infected person, aged in their 30s, has been isolated in hospital, she added.

Globally, coronavirus cases exceeded 10 million on Sunday, a major milestone in the spread of a disease that has killed more than half a million people in seven months.