Fellow Nationals MP Adam Marshall and MLCs Trevor Khan and Ben Franklin reportedly attended a restaurant in Paddington with Ms Cooke on Monday night and are now also in isolation.

"It is a Parliamentary sitting week, so being in Sydney was unavoidable," Ms Cooke said in a statement.

"I opened a text message from NSW Health shortly before 7am this morning advising me to take a Covid-19 test and self-isolate, and I immediately did so."

"I await the test results and further instruction from NSW Health."

NSW Health announced on Wednesday morning that 13 new coronavirus cases in south-east Sydney areas including 8 from a party involving a Bondi Junction worker.

NSW Premier Gladys Berejiklian said the state was facing a "very contagious [Delta] variant of COVID" in the that was transmitting between people in "very fleeting encounters".

From 4pm on Wednesday until July 1, local government areas in Greater Sydney, Central Coast, Blue Mountains, Wolllongong and Shellharbour will face new restrictions.

In those areas, masks will be mandatory in certain public indoor venues including retail, theatres and aged care facilities and on public transport.

Household visitors will be limited to five guests including children, indoor singing will be banned, and dance and gym classes will be limited to 20 people.

The one person per four square metre rule will be reinstated for indoor and outdoor settings, including weddings and funerals.

People who live and work in the City of Sydney, Waverley, Randwick, Canada Bay, Inner West, Bayside and Woollahra local government areas will not be allowed to leave metropolitan Sydney for non-essential reasons.

"We don't want the virus to spread into our regions," Ms Berejiklian said.

Ms Berejiklian said Regional NSW MPs would be expected to stay home after leaving Sydney.

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