Asked if closing the border every time a hotspot was discovered was a viable plan Mr Andrews said it "simply has to be".

"Every time I get public health advice to close the border I will close the border and I will do it within hours," he said.

Mr Andrews said when he received advice that there was a "deteriorating set of circumstances in Sydney" causing danger he had to act.

"The border will be closed for as long as the Chief Health Officer believes that proportionate and appropriate and whenever I get that advice in the future I'll make those tough decisions and we'll just have to make it work," he said.

IN OTHER NEWS:

"I apologise to those who are in queues to get tested, those who are in queues to get through a checkpoint but as difficult as that is and I appreciate it's very challenging but that's nothing compared to a third wave."

Only 15 locally-transmitted cases of COVID-19 were recorded in the 24 hours to 8am Monday, compared to 38 the day before. There were 38,000 tests undertaken.

However, Ms Berejiklian confirmed the source of the case which caused the spread remained unknown.

Ms Berejiklian called on all residents to wear masks on public transport and in other crowded areas.

Deputy Premier John Barilaro said there was anxiety in the region as people flock to communities for Christmas holidays.

He said there was no reason to panic in the region as the government was putting measures in place to protect communities