A surge in COVID-19 cases in Australia's second-biggest city could take weeks to subside despite a lockdown and orders to wear masks, Australia's acting chief medical officer said on Monday as the country braces for a second wave of infections.

The disease caused by the novel coronavirus flared up in Victoria state in July, mainly in Melbourne, with a daily record of 438 cases recorded on Friday.

Victoria's government has ordered about 5 million people into a partial lockdown for six weeks and told residents around Melbourne to cover their faces if they have to leave their homes.