Prime Minister Scott Morrison insists there will be plenty of masks to go around, with NSW residents also being urged to consider wearing them where social distancing is not possible.

Masks will be mandatory in Melbourne and the Mitchell Shire from Thursday in a bid to curb community transmission of the virus.

The Victorian government has ordered 1.37 million reusable masks to give out to teachers and students, on top of 1.2 million single-use masks.

The federal government is providing another million masks for Victorian workers in aged care and disability centres.

Victoria recorded 275 new coronavirus cases on Monday and another death, a woman in her 80s, bringing the national toll to 123.

Premier Daniel Andrews is confident strict lockdowns will be effective, so long as everyone follows the rules.

"We can't afford to ignore the absolute truth of what we face and that is that this virus is not yet contained," he said in Melbourne.

The prime minister said mask production had been ramped up to meet demand.

"It might require a bit of patience at the outset, when there's a bit of a rush on," he said.

"For the state government who has decided to make that mandatory, I have no doubt that they would have considered the supply issues when they made that decision."

Twenty new cases were confirmed in NSW, all linked to three growing clusters and returned travellers.

Premier Gladys Berejiklian said businesses had been given a week to comply with tougher restrictions, against her better judgment, but the full letter of the law would apply from Friday.

"Some businesses have been absolutely outstanding ... you can feel when you walk in the door, you can tell they are COVID-safe, but too many aren't taking them seriously enough," she said in Sydney.

She also asked people to limit non-essential travel, avoid crowds and "if you cannot guarantee people around you will respect that social distancing, you must wear a mask".

Deputy Chief Medical Officer Nick Coatsworth said a key example was public transport.

"The advice is to completely reconsider how you get to work, if that's possible, and avoid public transport.

"However, if you find yourself having to use public transport - and we acknowledge there are many, many Australians who travel to work using public transport - then we would encourage mask use."

Authorities are trying to trace a growing coronavirus cluster on the NSW south coast, with the Soldiers Club in Batemans Bay closed for two weeks after eight people tested positive.

Queensland recorded one new case of the virus while a suspected case in hotel quarantine in Tasmania is being investigated.

If confirmed it would be the first new infection in the island state in two months.

Australian Associated Press