Federal cabinet's national security committee will meet on Tuesday to finalise what lethal military equipment Australia will provide to Ukraine.
Prime Minister Scott Morrison said assistance given to Ukraine following the Russian invasion would be stepped up to include lethal aid, in line with support from other western nations.
The national security committee will receive reports on what lethal aid can be provided, following planning over the past day.
"The extent of what we announce will also be the subject of national security considerations," Mr Morrison told reporters in Brisbane on Monday.
"I don't want to flag there is ... a list of what we may provide, we'll consider that as we work through those issues, but the lethal aid support sees a step up again, together with the rest of the world."
Mr Morrison received a message from Ukrainian President Volodymyr Zelenskyy on Sunday night, with the pair potentially set to speak later on Monday.
Australia has already pledged $4 million in military assistance that will go to NATO's Trust Fund for Ukraine to support non-lethal military equipment and medical supplies.
"The Ukrainian people have shown tremendous strength and tremendous resolve, but the situation remains terribly concerning," Mr Morrison said.
"I am pleased that we've seen an accelerating and increasingly strengthened response from western democracies in standing up against what is thuggish brutality."
The federal government has also updated its travel advice to Russia, urging Australians not to go to the country and for citizens to leave as soon as possible.
The prime minister urged Ukrainians in Australia not to fly to Ukraine to fight in the conflict.
"I can understand, absolutely, the strong feelings and the motivations for people to go and do that," Mr Morrison said.
"At this time, the legality of such actions are uncertain under Australian law."
Australian-targeted financial sanctions and travel bans on Russian President Vladimir Putin and members of Russia's Security Council came into effect at midnight on Sunday.
Treasurer Josh Frydenberg said the sanctions the Australian government put in place last week had already had an effect on Russia's economy.
But he said it was "no secret" Putin had ambitions beyond invading Ukraine.
"Vladimir Putin starts with Ukraine, but who's next? That is the question," he told ABC Radio.
"This is the first major interstate conflict within Europe since the Nazis were defeated. This is a direct challenge to the international rules-based order that has underpinned prosperity in Europe for more than 70 years."
Labor frontbencher Jim Chalmers said Australia needed to do whatever was necessary to support Ukraine both financially and with weapons.
"The world should speak as one in supporting (Ukrainians), their courage, and their efforts," he told Sky News.
"Whether that is support with weapons (or) on the cybersecurity front, whether it is tightening the screws on the Russian economy - all of these things should be stepped up if they can."
Mr Putin has ordered his military command to put nuclear-armed forces on high alert as Ukrainian fighters defending the city of Kharkiv said they had repelled an attack by invading Russian troops.
It comes as plans are under way for a meeting between Ukrainian and Russian officials at the Belarusian-Ukrainian border.
