NSW recorded 415 new local cases of COVID-19 overnight to Sunday, following the entire state entering lockdown on Saturday evening.

NSW Premier Gladys Berejiklian said there had been a "disturbing" number of community transmission cases.

"Yesterday to 8pm we had 157,000 tests in SW, which is a healthy number and we encourage people to come forward and get tested," she said.

"However our community transmission numbers are disturbingly high. We had 478 cases of community transmission to 8pm last night and we can't stress enough how hard all of us have to work to reduce these numbers, to reduce the growth of the spread and make sure we are all staying home unless we absolutely have to do otherwise."

Seven people died from COVID-19 during the same period.

Ms Berejiklian expressed her heartfelt condolences to the families of those who died an said it was unfortunate that just two of them had received one dose of vaccine and the other were unvaccinated.

"We know the vaccines are working and it's important for all of us to protect our loved ones and ourselves by getting vaccinated but please know that when you do get vaccinated that it takes two to three weeks for the first dose to take effect," she said.

"Don't assume you are protected as soon as you get the jab, please assume you have the virus and everybody you come into contact with has the virus and follow the rules as strictly as you can."

An eight person, a teenager, has also died in NSW after the 8pm reporting period.

Monday marked the start of NSW Police Force's 'Operation Stay at Home' to enforce new restrictions, regional area entry permits and the statewide lockdown.

Ms Berejiklian said there would be a level of police enforcement "never seen before".

"It only takes a handful people to do the wrong thing to cause a setback for all of us," Ms Berejiklian said.

Deputy Premier John Barilaro said Dubbo and Walgett were the areas of greatest concern in regional NSW with 35 new cases overnight.

"My message for Dubbo, we all know how interconnected those regions are, is to please follow the health orders, the stay at home orders, and to minimise mobilisation," he said.

Mr Barilaro said the Hunter and New England region was stabilising with 16 new cases but they were all from a known source of infection.

"If we follow the rules, stay home and do the right thing, we can come out of this lockdown soon," he said.

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