All Victorians travelling on flights to the ACT will be denied entry to Canberra from Tuesday, following a surge in coronavirus cases in Melbourne.
ACT residents returning from any part of Melbourne will have to quarantine for 14 days from 11.59pm Monday.
Chief Minister Andrew Barr said the move would coincide with the closure of the NSW and Victorian border, which will come into effect at 12.01am Wednesday.
The decision was made to close the border after 127 cases of COVID-19 were recorded in Victoria in the 24 hours to Monday, the highest daily rate of increase in the state.
However, the travel restriction to Victorians will not impact the easing of restrictions in the ACT, with the third stage enacted from Friday.
People coming into the ACT from known coronavirus hotspots in Victoria on flights had been ordered to self quarantine for 14 days at their own expense or return home.
That will be expanded even further from 11.59pm Monday, with anyone from Melbourne ordered to quarantine should they arrive in the capital.
From 11.59pm on Tuesday, it will then apply to all Victorians.
Residents from NSW or the ACT who are returning to Canberra from Victoria will be able to return home but will have to self-quarantine for 14 days.
"These measures will be further enhanced from midnight on Tuesday, where anyone from Victoria will be denied entry unless they are granted an exemption by the NSW or ACT government," Mr Barr said.
"This will significantly reduce the likelihood of the virus spreading from Victoria into the Canberra region."
The Chief Minister said the measure barring Victorians from the ACT was temporary and would be in place as long as the NSW and Victorian border was closed.
"It's important we do everything we can and at the same time, support Victoria in stopping the spread," Mr Barr said.
"Doing so now will enable the territory to continue to implement our recovery plan."
Changes to stage three of coronavirus restrictions are set to be minor, with the one person per four square metre rule expected to remain in place.
"We will be moving cautiously, given what is happening in Victoria," Mr Barr said.
Exemptions may be granted by the ACT and NSW governments for people travelling for essential or compassionate reasons.
"The ACT will strive for consistency with the NSW system," he said.
"What all of this demonstrates is this pandemic is not over.
"Outbreaks of the virus are a real possibility."
Health Minister Rachel Stephen-Smith on Monday extended the ACT's public health emergency declaration in response to COVID-19 for a further 45 days.
It allows the chief health officer to continue to give any direction, deemed necessary to protect the community from the spread of COVID-19.
"We have responded incredibly well to COVID-19 so far and are in a good position. However, we know COVID-19 continues to pose a significant risk to public health and the ACT community," Ms Stephen-Smith said.
Anyone disembarking from Melbourne fights at Canberra Airport will have their identification checked.
A spokesman for the airport said it was still waiting for advice from the ACT government about how the ban on Melbourne travellers would work on the ground.
There are two Qantas and one Virgin flight from Melbourne due to land in Canberra on Tuesday.
There are already ACT Health officials at the airport for incoming flights. How the new arrangements would work is unclear. In the case of flights to Queensland, passengers need prior permission.