ACT Health has confirmed the Wollongong local government area remains included in the quarantine area but the broader Illawarra-Shoalhaven region is not included. The broader Illawarra-Shoalhaven region was inadvertently included in Sunday's announcement, but ACT Health corrected this on Monday morning.

The quarantine requirements would cover anyone travelling from Greater Sydney, Central Coast and Nepean Blue Mountains.

Health Minister Rachel Stephen-Smith announced on Sunday afternoon that the quarantine period would be 14 days.

Returning ACT residents will be able to quarantine at home.

ACT chief health officer Kerryn Coleman signed the public health direction on Sunday to make the new arrangements legally enforceable.

"This is not about stopping ACT residents coming home," Dr Coleman said.

A further 15 cases were recorded in NSW to 8pm Sunday, all linked to the northern beaches cluster.

There are now 83 cases linked to that cluster.

NSW Premier Gladys Berejiklian said the state remained in a volatile situation.

"The government is monitoring the situation almost on an hourly basis. We will consider our position in relation to what Christmas and the next few days look like beyond Wednesday," she said.

Ms Stephen-Smith said people who were not ACT residents should not travel to Canberra if they had been in Greater Sydney, Central Coast and Nepean Blue Mountains.

Those who come to the ACT will be required to quarantine, and anyone staying at the same premises will also be required to quarantine.

ACT Health said it would not consider exemption requests for non-residents coming from Greater Sydney, except in extreme extenuating circumstances.

Travellers from Greater Sydney, Central Coast and Nepean Blue Mountains are required to notify ACT Health in advance of their arrival by completing an online declaration. The form is available on the ACT COVID-19 website .

Dr Coleman warned the community to be prepared for the restrictions to continue over Christmas and the New Year period.

Ms Stephen-Smith also encouraged Canberrans not to travel to Greater Sydney and urged them to reconsider their need to travel within wider NSW.

She said anyone considering travelling to any jurisdiction in Australia should monitor its border and quarantine requirements, and warned that these could change quickly.

"Many jurisdictions are perfectly reasonably treating the ACT as if it is part of regional NSW," Ms Stephen-Smith said.

"If we start to see this cluster and this outbreak seeding outside of Greater Sydney into wider regional NSW it is quite possible that the ACT would be caught up in that and we would be subject to restrictions from other jurisdictions," she said.

The NSW government has tightened its own coronavirus restrictions after a COVID-19 cluster in Sydney ballooned to 70 cases, but its chief health official said it may never be able to find the source.

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NSW recorded another 30 cases in the 24 hours to 9am on Sunday with 28 linked to the cluster on Sydney's northern beaches.

Anyone who has visited the northern beaches from Friday December 11 is legally required in the ACT to self-quarantine for 14 days from the date they were last there and get tested, even if they do not have symptoms.

People must stay in quarantine for the whole 14 days, even if they have a negative test result.

Demand for COVID-19 testing has increased and the territory government recorded 999 tests in the 24 hours to 6pm Sunday.

"We thank everyone for coming out and getting tested appropriately but please be patient and treat our workers with respect," Dr Coleman said.

The ACT government will consider expanding testing hours.

It had announced restricted testing hours over the Christmas period, however Dr Coleman said health officials were now in discussions over whether these would be adequate given the spike in demand.

Dr Coleman also said there was the potential to roll out pop-out testing sites if required.