London, June 28: Australian leaders will hold an emergency meeting on Monday after a spike in Covid infections.

An outbreak in Sydney linked to the highly contagious Delta variant has grown to 128 cases. Cases have also been recorded in the Northern Territory, Queensland and Western Australia.

Officials say it is a "critical time" for the country, which has kept case numbers low with border closures and lockdowns. 

This is the first time in months that cases have emerged in multiple parts of the country at the same time. "I think we're entering a new phase of this pandemic, with the more contagious Delta strain," Treasurer Josh Frydenberg told ABC News on Monday.

The escalation in Covid infections has prompted lockdowns in the cities of Sydney and Darwin, as well as restrictions across four states. The situation remains most concerning in Sydney, where some five million residents are subject to a stay-at-home order.

The New South Wales (NSW) state government on Sunday expanded a lockdown to cover all of Greater Sydney, the Blue Mountains, Central Coast and Wollongong.

Sydney residents queued to get tested at this drive-through clinic at Bondi Beach, GETTY IMAGES

Many businesses and venues have been ordered shut.

NSW Premier Gladys Berejiklian on Monday reported 18 new cases, down from the 30 reported the previous day. Nearly 59,000 people had been tested in the past 24 hours.

"We have to be prepared for the numbers to bounce around and we have to be prepared for the numbers to go up considerably because, with this strain, we are seeing almost 100% of transmission within households," she said.