The news came as the ACT was once again coronavirus-free after no new cases were reported in the past 24 hours and the most recent case recovered.

ACT chief health officer Kerryn Coleman said authorities remained concerned about Sydney's coronavirus cases, specifically a new cluster that has emerged from a bottle shop in western Sydney.

NSW reported four new cases on Tuesday, two of which were flagged on Monday as linked to the Berala BWS outbreak.

"We have been closely monitoring the situation in NSW and what has been unfolding there over the past few days," Dr Coleman said on Tuesday morning.

"The recent Berala cluster in Sydney's west is particularly concerning and another example of how quickly and easily the virus can spread."

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The announcement means non-residents who have been in the designated hotspots will continue to be banned from entering the ACT until at least Wednesday, January 13.

ACT residents from those areas are allowed to come home, but still need to notify ACT Health of their intention to return via an online declaration form and enter quarantine for 14 days on arrival.

More than 2700 people were in quarantine after returning from NSW hotspots as of Tuesday morning.

Chief Minister Andrew Barr issued a stern warning to people who tried to enter the ACT from hotspot areas, saying those found here illegally would face fines of up to $8000.

Mr Barr said border checks would continue on the Federal Highway and other entry points to the ACT.

But police would also ramp up enforcement inside the ACT's border, with a breathe-testing style operation to target NSW number plates on main roads such as Adelaide Avenue, Northbourne Avenue and Canberra Avenue.

Chief Police Officer Neil Gaughan said officers would also target popular tourist attractions in the parliamentary triangle.

Police said on Monday that a request for assistance at the border checkpoints had been made to ACT Emergency Services and the Australian Defence Force.

But Mr Barr said while the ADF might help with some logistical support "around the edges", they would not be involved in enforcement.

"People should not expect to see the army at the border between ACT and NSW," he said.

Mr Barr said the compliance crackdown would be an inconvenience for some, but insisted the rules were in place for a reason.

"Don't take the risk of an $8000 fine," he said.

"Don't put your health, the health of the people you are visiting or the places you are staying and this broader community at risk. Don't do it."

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