Canberrans returning from Victoria will be forced to self-isolate on arrival and non-residents in Melbourne have been told not to travel to the ACT.
ACT Chief Minister Andrew Barr said the Victorian lockdown, announced by Premier Daniel Andrews earlier on Friday, was a proportionate and appropriate decision.
Canberrans who return to the ACT from Victoria after midnight on Friday will be required to isolate for the length of the lockdown, currently set at five days. However, that situation could change.
Travellers who arrived into Canberra from Melbourne airport on February 7 and 8 will be asked to identify themselves, go into isolation and get tested after Tullamarine airport was declared a hotspot.
ACT Chief Health Officer Dr Kerryn Coleman said Jetstar's terminal 4 on February 9 was a site of a particularly high risk and exposure was at its height between 4.40am and 2pm.
Anyone who is a household contact of someone who visited terminal 4 on February 9 in these times should also stay in isolation until that person receives a negative result, health authorities said.
Jetstar does not fly into Canberra so this risk would only apply to passengers who were at this terminal, then transferred to another terminal and travelled on to the ACT, either by air or some other means.
The planned easing of coronavirus restrictions across the ACT was put on hold on Friday in the wake of a virulent outbreak and subsequent snap five-day lockdown announced for Victoria, starting at midnight.
"Clearly this is going to be very hard for Victorians and for Canberans who have families in Victoria," Mr Barr said.
"It is not a surprise. I did say at the beginning of the year that 2021 would look a lot like 2020."
"With vaccines coming we would hope that we would not be in this situation in the second half of the year. For now these measures are necessary, proportionate and appropriate."
Victorian members of federal parliament have been told to get to Canberra immediately, or face being locked down and unable to leave. The next parliamentary sitting week begins on Monday.
Dr Coleman reiterated that federal parliamentarians were considered essential workers, but would have to apply for an exemption if they arrived in Canberra from Victoria after midnight on Friday.
Stage 4 restrictions will be in place across Victoria until midnight on Wednesday. There will be mandatory mask-wearing across the state and all schools will be closed.
There are now 13 coronavirus cases linked to Melbourne's Holiday Inn, after five new cases were confirmed on Friday.
NSW is not closing its border as yet but Queensland will close its borders to Victoria for two weeks, effective from 1am Saturday. Tasmania has also declared Victoria "high risk" and will deny entry to travellers.
"We will be reviewing our position after monitoring what is happening in Victoria," Mr Barr said.
Mr Barr said the government was expecting to review lifting its capacity limits for larger entertainment venues and events across Canberra but that had now been put on hold in light of the Victorian outbreak and subsequent lockdown.
"Should our position remain stable in the coming days ... if we don't see an increase in risk, and they [Victoria] emerge from their lockdown in the middle of next week without further significant outbreaks, we may be in a position to announce further and hopefully ongoing easing of restrictions related to those areas we identified," he said.
"We'll have a look next week once we have more information from Victoria."