At least 57 of the 356 cases detected to 8pm on Monday were not isolated during their infectious period, 40 were isolated for part of their infectious period, and the status of 157 remain under investigation.

A total of 95,000 tests were carried out across the state on Monday, following a record 133,000 tests performed on Sunday, premier Gladys Berejiklian said.

Tamworth entered a seven-day lockdown at 6pm on Monday after a number of exposure sites were identified, and the NSW Northern Rivers region will go into a similar lockdown at 6pm Tuesday after positive cases emerged in Byron Bay.

In other news

Several uni students have been fined thousands of dollars after police began investigating a party believed to have been attended by up 40 people at Wagga's Charles Sturt University campus last month.

The group scattered when security guards arrived, police said, and inquiries are continuing to identify further attendees.

A man in his 80s from south west Sydney has died in Liverpool Hospital, after acquiring his infection as part of the outbreak at that hospital, taking the toll from that outbreak to six.

A woman in her 80s from south west Sydney also died at that hospital, unlinked to the outbreak, and a man in his 70s from western Sydney died in Nepean Hospital.

A man from northern NSW, who was aged in his 80s, has passed away in the Royal Prince Alfred Hospital. He acquired his infection overseas and is not linked to the current outbreak, chief health officer Kerry Chant said.

Victoria has announced 10 new cases and Queensland has found three more linked to the Brisbane cluster, but positive news has been found in zero cases for the newly-locked down Cairns region.

When 6pm arrives on Tuesday, the Northern Rivers joins Tamworth, Armidale, Newcastle and the Hunter Valley and Greater Sydney in lockdown.

Wagga's leaders are urging residents to be vigilant after it was revealed another Tamworth would be locked down, and the state recorded another 283 confirmed COVID-19 cases, on Monday.

"It's not a matter of if, it's a matter of when," mayor Greg Conkey said.

"We are the largest rural and regional city, we have done well up until now, but I have a feeling it will come here at some stage."

Wagga MP Joe McGirr reiterated the importance of keeping COVID-19 out of regional NSW, adding the virus doesn't travel unless people travel.

"As the recent case of a COVID-positive young woman from Newcastle visiting Tamworth demonstrates, it only takes one person to spread this virus," he said.

That woman has since spoken out on social media, saying she is a Tamworth girl who visited family one day and went home the next. She didn't know she was infectious.

"I was not in lockdown, I was not a close contact and I had no symptoms on Thursday," she said, while pleading for kindness.

"There was nothing to stop me from visiting my family and friends in Tamworth. I am a Tamworth girl. What happened to country hospitality? What happened to looking after your neighbour?"

More on the pandemic:

The hardened restrictions for Byron Shire, Richmond Valley, Lismore and Ballina Shire local government areas come after a man stayed in the Byron area after travelling to Sydney in late July and moved around in the community for some days.

He had no recorded QR code check-ins during his infectious period.

Our journalists work hard to provide local, up-to-date news to the community. This is how you can continue to access our trusted content: