People in Melbourne must now wear masks when leaving their homes as Victoria, Australia's second most-populous state, marked two weeks of triple-digit increases in new coronavirus infections on Sunday.
Melbournians not wearing face coverings will be fined A$200 ($140), said Victoria Premier Daniel Andrews.
Victoria, which has forced nearly 5 million people into a partial six-week lockdown on July 9, reported 363 new cases of the coronavirus on Sunday, after 217 cases the previous day.
"We're going to be wearing masks in Victoria and potentially in other parts of the country for a very long time," Andrews told a televised briefing.
"There's no vaccine to this wildly infectious virus," he said. Masks are "a simple thing, but it's about changing habits, it's about becoming a simple part of your routine."
Australia has recorded about 11,800 cases of COVID-19, a fraction of what has been seen in other countries or even some US states, but an outbreak of community transmission in Victoria has been growing, prompting authorities to restrict social distancing.
Three COVID-19 deaths were reported in Victoria on Sunday, bringing the total to 38 and raising Australia's death toll to 121.
New South Wales, the most populous state, has seen new cases in the low double digits in recent weeks and growing. Health officials are concerned about the transmission rate, which they say is higher than in Victoria.
About 60 people in Sydney face a fine of $1,000 each after attending a party Saturday night and breaking the public health guidelines of no more than 20 visitors to a home, police said.