Millions in Sydney began their harshest lockdown since the pandemic began on Friday as Covid-19 cases spiked to record levels in Australia's largest city with state and national leaders set to meet to discuss the country's reopening plans.

With Sydney, the capital of New South Wales state, struggling under record surge of cases, officials toughened curbs across eight local council areas, where most new infections were being reported, and sought the military's help to enforce lockdown rules.

More than two million affected residents must stay within 5km of their homes and have to wear masks when they step outside, meanwhile police have been given sweeping new powers to close businesses flouting rules.