Pressure is mounting on Tony Abbott to push for a ban on President Vladimir Putin attending the Brisbane G20 meeting after Moscow moved troops and tanks into neighbouring Ukraine.
The Prime Minister condemned Moscow in scathing terms on Friday, branding the stream of Russian soldiers and weapons into eastern Ukraine an apparent "invasion" and calling the actions "utterly unacceptable".
Opposition Leader Bill Shorten called on Mr Abbott and Foreign Minister Julie Bishop to talk to other G20 member nations about banning Mr Putin from attending the leaders' meeting in November.
"It is probably time for the Prime Minister and the Foreign Minister to be talking to other nations ... about whether it is appropriate for Mr Putin to come to Australia," he said. "Following the tragic events of MH17, the complete lack of remorse or responsibility, the lack of full co-operation ... and now scenes of thousands of Russian soldiers flooding across the Ukrainian border, I think most Australians have grave reservations about welcoming Mr Putin to Australia."
The comments come six weeks after 298 people including 38 Australian citizens and residents were killed in the downing of the Malaysian Airlines flight MH17, widely believed to have been caused by pro-Moscow Ukrainian separatists firing a surface-to-air missile supplied by Russia.
After NATO reported that at least 1000 Kremlin troops had crossed into Ukraine and another 20,000 were massing on the Russian side of the border, a furious Mr Abbott went further than other world leaders and branded the movements an invasion.
"Clearly if, as seems to have been the case, Russian armed forces have simply moved across the border, that is an invasion and it is utterly reprehensible," he said. "It is an absolutely clear-cut case of a larger country bullying a smaller country, and this should have no place in our world.
"You cannot have an international order if might is right. You cannot have a safe and secure world if powerful countries are able to take what they want ... It is completely absolutely and utterly unacceptable."
It is unlikely Australia would unilaterally block Mr Putin from attending G20. Rather, any ban would likely have to win the support of other leading members nations including the US, Britain and China.
NATO has released satellite images purporting to show Russian troops, tanks, artillery and other military hardware streaming across the border into eastern Ukraine. NATO Brigadier General Nico Tak told the BBC that about 1000 Russian troops were inside the country, fighting in support of the pro-Moscow separatists.
He said there had been a "significant escalation in the level and sophistication of Russia's military interference in Ukraine" over the past two weeks.
"[NATO has] detected large quantities of advanced weapons, including air defence systems, artillery, tanks, and armoured personnel carriers being transferred to separatist forces in eastern Ukraine," he said.