New South Wales has recorded five new cases of COVID-19 overnight.

The new infections include two people in hotel quarantine and three of which are in south-west Sydney.

None of the new cases are linked to the security guard who tested positive, which Premier Gladys Berejiklian has described as "good news".

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Ms Berejiklian said the state is still "on high alert to make sure that there aren't any additional transmissions that we're not picking up."

"Please make sure, if you're in western or south-western Sydney in particular, that if you have the mildest of symptoms, you come forward and get tested, because we know the virus is circulating in those communities and our anxiety is that we want to reduce the number of unknown cases."

Ms Berejiklian defended her ongoing decision to close the NSW-Victoria border after being asked about the border permits.

"The last thing that I would want to see is the disease seeding in rural and regional NSW," she said.

"Everything we do is to protect our community, to keep our community safe. I appreciate the challenges that are involved but consider the alternative.

"Consider the virus seeping into our regions and that is something that I don't stand for, and we need to make life as easy as possible for those communities suffering on the borders."

Ms Berejiklian added "it would be courageous to predict beyond a few months" when asked when the border may reopen.

NSW in 'critical phase' of  fight against COVID-19

Despite the low number of cases, NSW Chief Health Officer Dr Kerry Chant has reiterated "this is an incredibly critical phase in our response".

"We are seeing these continual low levels of transmission, particularly in south-western Sydney, but also popping up in western Sydney from time to time," Dr Chant said.

"It's critical that we continue to see those high testing rates. It's important that the community continues to embrace those COVID-safe behaviours, such as social distancing and wearing a mask when you can't socially distance."

The state's total number of coronavirus cases is 3782.

There are currently 111 COVID-19 cases being treated by NSW Health. Of these, eight COVID 19 patients in intensive care and five are ventilated.

Police have been door-knocking in south-west Sydney

Ms Berejiklian said police have been doing random checks on people self-isolating in south-west Sydney and people have largely been doing the right thing.

"The police are already doing those checks and compliance is very high," she said.

When asked about random testing in communities where there is an outbreak, the premier said, "it doesn't work".

"Random testing is less effective than targeting specific communities who are demonstrating symptoms or who have been exposed."

Source: 9News