Foreign Minister Penny Wong has used her speech to the UN General Assembly meeting to label Vladimir Putin's nuclear threats "weak and desperate", while calling on China and the global community to ramp up pressure on Moscow to end its invasion of Ukraine.
Australia has been a forceful critic of Russia's invasion and has been providing Ukraine with military equipment.
Senator Wong intensified her criticism in the wake of Mr Putin's announcement earlier this week that Russia will mobilise hundreds of thousands of people to fight in Ukraine after suffering a series of military setbacks.
"We cannot accept a situation where large countries determine the fate of smaller countries. That is why Russia's illegal, immoral invasion of Ukraine cannot be normalised and it cannot be minimised," Senator Wong said on Friday.
"Russia's attack on Ukraine is an attack on all smaller countries. It is an assertion that a larger country is entitled to subjugate a smaller neighbour — to decide whether another country can even exist."
During a brief press conference, following her appearance on the world's most-watched diplomatic stage, Senator Wong underlined her message that Australia had an important role to play in maintaining peace.
"Small and medium sized powers shouldn't just leave it to the big powers to sort out," she said.
"We have agency."
Mr Putin made thinly veiled threats to use nuclear weapons when announcing the partial mobilisation, saying Russia would "certainly make use of all weapon systems available to us" if its "territorial integrity" was threatened.
Senator Wong has repeatedly labelled his warning "unthinkable". She told the General Assembly on Friday it was also a reminder of the dangers posed by nuclear weapons.
"Mr Putin's weak and desperate nuclear threats underline the danger that nuclear weapons pose to us all, and the urgent need for progress on nuclear disarmament," she said.
"Australia has always pursued a world without nuclear weapons, and we will redouble our efforts towards this goal — and to strengthening the non-proliferation regime."
On Friday morning, UN-appointed human rights investigators concluded war crimes have been committed in Ukraine by Russian troops since the war began in February.
After a seven-month inquiry, the three-person panel determined allegations of civilian executions, torture and sexual violence, including against children, to be true.
Senator Wong told journalists she was not aware of the findings prior to delivering her speech, but condemned such acts of violence as "unacceptable"
"The international community can choose to work together to hold Russia to account and we should," she said.
Foreign minister urged China to ramp up pressure on Moscow
The foreign minister also took aim at Russia's conduct at the United Nations during the war in Ukraine.
Earlier this year Russia used its position as a permanent member of the United Nations Security Council to block a resolution denouncing its invasion of Ukraine, while China abstained.
Senator Wong suggested that Russia's actions risked undermining the credibility of the body.
"It was never intended that the Security Council veto power would be used to enable unchecked abuse of the UN charter — by the very countries that were given the veto," the foreign minister said.
Separately, she reiterated that Australia backs reform of the Security Council to ensure "greater permanent representation for Africa, Latin America, and Asia, including India and Japan."
She also briefly called once again on Beijing to ramp up pressure on Russia to bring the war to an end.
"It is especially important for countries that play leading roles in international fora, and countries with influence on Russia, to exert their influence to end this war," she said.
"In this pursuit, the world looks to China, a great power, a Permanent Member of the Security Council, with a "no limits partnership" with Russia."
