Defence Minister Peter Dutton has warned of "bloody scenes" if Russia invades Ukraine, but says no request for assistance has been sought by the eastern European nation.
Mr Dutton said it was unlikely Ukraine would reach out to Australia for direct military assistance, after Foreign Minister Marise Payne again ruled out military aid.
"We haven't received a request for assistance and we wouldn't expect to receive one," Mr Dutton told Sky News on Tuesday.
"Australia's responsibility is within our region. We have a lot going on in the Indo-Pacific."
But the defence minister said it was important free nations stood their ground in the face of authoritarianism.
"It is important to call out dictators and people who have aggression as their first instinct. It's unacceptable," he said.
"At the moment, we hope that deterrence can mean that the Russians step back and they don't continue on a path to conflict. Tens of thousands of people will die, there will be bloody scenes."
His comments came as the Australian embassy in Ukraine is contacting citizens, urging them to leave immediately.
Senator Payne said there were about 1400 Australians in Ukraine and they should use commercial means to leave the country if safe to do so.
"This is a cautious and prudent step because the security situation is unpredictable," Senator Payne told the ABC.
"It is about protecting Australians on the ground."
The Department of Foreign Affairs and Trade on Monday night raised its advice to "Do Not Travel".
"Australians in Ukraine should leave now by commercial means, where safe to do so, noting that flight availability could change or be suspended at short notice," it said in a statement.
"Australians who decide to remain in Ukraine should review their personal security plans, be prepared to shelter in place if required, maintain heightened security awareness and register with DFAT."
Senator Payne said the decision by DFAT was sparked by consultations with "like-minded counterparts in Kyiv and on the subject of Ukraine".
"But importantly this decision doesn't change one iota our steadfast support for Ukraine sovereignty and territorial integrity."
Labor leader Anthony Albanese said de-escalation was necessary.
"We have called for Russia to respect Ukraine's sovereignty and for a de-escalation ... leadership is sometimes about just saying people need to cool it," he told reporters in Canberra.
Ukrainian diplomat in Australia Volodymyr Shalkivskyi urged people not to panic, saying pulling people out of the country "sends the wrong message".
"We would like to avoid panic and rumours that the invasion is inevitable," the Ukrainan embassy's Charge d'Affaires told the ABC.
"The official responsibility of Australian and Ukrainian officials is to facilitate and assist in every possible way. But in this situation we would like to avoid panic and different kinds of rumours that the invasion is inevitable."
Tensions in Ukraine have been increasing for months after the Kremlin massed about 100,000 troops near Ukraine's borders, a build-up the West says is preparation for a war to prevent Ukraine joining NATO.
The Kremlin has repeatedly denied planning to invade.
While ruling out military assistance, Senator Payne said Australia will consider providing cyber security support.
"There has been a significant cyber attack already on Ukraine, understood to have come from potentially Russian sources," she said.
"Australia has been working closely with partners in the international community, including with Ukraine, on cyber resilience and cybersecurity, and if Australia can assist in that regard we will."
Mr Dutton wouldn't comment on whether Australia would employ offensive cyber attacks.
Further sanctions are also under review.
Australian Associated Press
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