SYDNEY, July 30 (Reuters) - 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 5 km (3 miles) 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. read more These tough curbs do not apply for other Sydney suburbs where residents can travel outside their suburbs for essential work, education, grocery and medical reasons. New South Wales clocked its biggest one-day rise in new infections on Thursday, with 239 cases. Officials have warned the situation "would get worse before getting better." Friday"s cases are expected to be released at 11 a.m. local time (0100 GMT). As Sydney heads into its sixth week of an extended lockdown, due to run until Aug. 28, the country"s national cabinet - the group of national and state leaders - will meet later in the day to discuss the country"s exit strategies from the pandemic. Australia has handled the coronavirus crisis much better than many other developed countries, with just under 34,000 cases and 923 deaths, but has been among the lowest in administering vaccination doses. With about 18% of people aged over 16 fully vaccinated so far, Australia"s immunisation drive hit several roadblocks due to changing medical advice for AstraZeneca (AZN.L) doses over blood clot concerns and supply constraints for Pfizer (PFE.N) shots. Queensland state, meanwhile, is on alert after a 17-year-old school student contracted the virus baffling officials. "(This) is quite concerning because I"m struggling to understand how she has acquired it," state Chief Health Officer Jeanette Young told reporters.