A Southern NSW Local Health District spokesperson said the six new diagnoses were in addition to the Sydney father and son who were at the club on Monday, July 13 and who subsequently returned home and tested positive.

Meanwhile, Sydney residents are being urged to avoid public transport and social gatherings as case numbers increase.

Victoria recorded its second highest daily infection toll over the weekend, despite strict lockdowns measures which have been in place for almost two weeks.

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

NSW Police Minister David Elliott said there were particular concerns for the south coast community.

"The concern in Batemans Bay is the ageing population down there and the transient nature over the school holidays of the population," he told the Seven Network on Monday.

"Make sure you don't put yourself in a position or situation where you can pass [the virus] on."

Anyone who was at the soldiers club between 7pm and 9.30pm on July 13 is urged to immediately self-isolate and seek testing. Even those returning negative tests must remain in isolation for two weeks.

Further, anyone at the club on Wednesday, July 15, Thursday, July 16 and Friday, July 17, is also urged to get tested and isolate.

"NSW Health is in the process of conducting further contact tracing of staff and patrons who were at the Batemans Bay Soldiers Club between 7pm to 9.30pm on Monday 13 July 2020," a Southern Health spokesperson said.

"In addition to the two people who were infectious with COVID-19 and were dining at the bistro, a further six people associated with the club have been diagnosed as positive with COVID-19.

"As a result, all patrons and staff who were at the Batemans Bay Soldiers Club on Monday 13 July, Wednesday 15 July, Thursday 16 July and Friday 17 July, should self-isolate for 14 days after they were last at the club, and seek testing for COVID-19.

"Even if they test negative, they should remain in isolation for the full 14 days, and should be tested again if they develop symptoms of COVID-19. Guidance for self-isolation for close contacts is available at https://www.health.nsw.gov.au/Infectious/factsheets/Pages/advice-for-contacts.aspx

Acting chief medical officer Paul Kelly expects it will be several weeks before Victorian case numbers reduce to single figures.

Professor Kelly says he has no regrets about not recommending Melburnians wear masks sooner.

While masks will be mandated in Melbourne and Mitchell, he says it's up to individuals if they want to wear one in other parts of the country.

"We've got a very different situation in Melbourne now where we have community transmission which is continuing to grow," he told ABC radio.

"This is another step that has been put into place in that context."

Hundreds of extra Australian Defence Force personnel will hit the ground in Victoria this week to help the state's fight against coronavirus.

An extra 272 ADF personnel will join 1200 already helping with border controls and contact tracing.

The federal government is also providing one million more masks for Victorian workers in aged care and disability centres, plus five mobile virus testing teams.

Health Minister Greg Hunt apologised to people inconvenienced by the mask-wearing rules.

"We are sorry that it has reached this point for all those who are affected," he told reporters.

"But this is about saving lives and protecting lives."

Victoria recorded 363 new coronavirus on Sunday and another three deaths, two men and a woman all in their 90s, bringing the state toll to 38 and the national figure to 122.

NSW confirmed 18 new cases in the 24 hours to 8pm on Saturday, with Mr Hunt acknowledging the state was facing a "Herculean tracing task".

NSW is imposing harsher border restrictions with Victoria, tightening the permit criteria for southerners wanting to go north.

On Friday evening, Southern Health was urging anyone at the club on July 13, to get tested, but that advice conflicted with advice from the deputy NSW health commissioner the following day. NSW Health on Saturday, was urging people to self-isolate, but only seek testing if they developed symptoms.

The Batemans Bay Post understands some seeking tests on Saturday were turned away or faced long waits.

"SNSWLHD is urging anyone feeling unwell - even with the mildest of symptoms such as a runny nose, scratchy throat cough, fever, shortness of breath, headache, sore throat, tiredness, loss of taste/smell, nausea, diarrhoea or muscle aches - to self-isolate and seek COVID-19 testing, so cases in the community are identified as quickly as possible," the spokesperson said on Sunday night.

"To ensure people can get tested quickly, SNSWLHD will continue testing in Batemans Bay through a COVID-19 pop-up clinic at the Hanging Rock Oval Car Park (near the function centre) on Beach Road, Batemans Bay.

"The clinic will be open from daily from 9am to 2pm until further notice. In anticipation of the continued demand, extra staff will be working at the Pop-up clinic during this time.

"The need for scheduled appointments across many of the District's COVID-19 testing sites has been removed. Callers to the SNSWLHD 1800 999 880 COVID line will be provided with information on testing eligibility and clinic times and locations.

"These sites include Goulburn Base Hospital, Queanbeyan District Hospital, Eurobodalla Health Service (Moruya), South East Regional Hospital, Cooma District Hospital, Jindabyne Clinic and Yass District Hospital.

"Also included are the 'pop-up' clinics at Malua Bay, Hanging Rock, Merimbula and Crookwell. This information is also available at www.snswlhd.health.nsw.gov.au

"A number of our smaller COVID testing sites will still be by appointment only (Pambula Hospital, Bombala MPS, Eden, Perisher and Thredbo) - call 1800 999 880 (option 2).

"It remains essential that everyone maintains social distancing and good hygiene to minimise the risk of spread between people. There are steps we can take to protect ourselves and loved ones:

"People can unwittingly pass it to others if they are incubating the infection or have very mild symptoms, so we all need to be very careful and practise hand hygiene and maintain social distancing by keeping at least 1.5m away from other people," the spokesperson said.

with AAP