Ukraine crisis: Tony Abbott, Julie Bishop, Bill Shorten condemn Russian 'invasion' as NATO images show troops across border

Prime Minister Tony Abbott has labelled the apparent presence of Russian forces in Ukraine's territory an "invasion" and says it is "utterly reprehensible".

NATO has released satellite images which it says show Russian combat forces, armed with heavy weapons, engaged in military operations in Ukraine.

It said well over 1,000 Russian troops are operating inside Ukraine, marking a significant escalation of Moscow's military involvement there.

Russia's ambassador to the EU, Vladimir Chizhov, has rejected the allegations but Mr Abbott says Russia is now "stepping out of the shadows".

"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 told reporters in Canberra.

"It is an absolutely clear-cut case of a larger country bullying a smaller country and this should have no place in our world.

"It is completely, absolutely and utterly unacceptable."

The United States has accused Russia of lying and deliberately fuelling the conflict in the region.

President Barack Obama, speaking to reporters overnight, did not use the term "invasion", instead calling it a continuation of what has been happening for months.

But Foreign Minister Julie Bishop said Russia's actions are a clear breach of international law and Australia will consider what action it can take to send a very strong message to Russia.

"It's against international norms, it's interfering in the domestic affairs of another country," she said.

"It is an invasion of Ukraine's sovereignty, a breach of its territorial integrity."

Russia are in it up to their eyeballs: Shorten

Opposition Leader Bill Shorten said Russia must be held accountable for its actions.

"The Russians are ... up to their eyeballs in this latest violence. It is a clear breach of international law," he told reporters in Melbourne.

"I think the language has moved. President Obama's called it an incursion, others have called it an invasion.

"I know what I would think. If the troops of another country were within the borders of my country, I would regard it as an invasion and a hostile act."

Professor Paul Dibb from the Australian National University says Russia's movements should be called for what it is.

"We can use splitting hairs as to whether it's a whole-scale invasion or an incursion. I think our politicians are correct. It's not a full-scale invasion of the whole of Ukraine but that's rather semantic frankly," he said.

"It is actually an invasion across the borders of an independent state - and that's the problem."

Russian president Vladimir Putin is scheduled to visit Brisbane in November for the G20 summit.

Mr Abbott said he expected G20 members will discuss whether Mr Putin should be banned from attending the meeting.

"Because he would be coming for a critical international gathering, it's not a decision which Australia really has a right to make unilaterally," Mr Abbott said.

"Nevertheless, it is an important question and it's one that I'll be weighing and I suspect a number of other countries will be weighing in the weeks ahead."

Mr Shorten said he has the "greatest reservations" about Mr Putin coming to Australia.

Death toll hits 2,593: United Nations

The United Nations today said 2,593 people, including civilians as well as Ukrainian and separatists combatants, had been killed in the conflict since mid-April.

Senior UN human rights official Ivan Simonovic said the death toll has continued to rise.

"The trend is clear and alarming. There is a significant increase in the death toll in the east," he told journalists.

"The current number of killed is 2,593 - close to 3,000 if we include the 298 victims of the [Malaysia Airlines] MH17 plane crash."

Mr Simonovic, who was presenting a report by a UN monitoring mission, said civilian casualties would continue to rise "as each side increases its strength, through mobilisation, better organisation or the deployment of new fighters and more sophisticated weapons and support from outside".

The death toll was nearly 400 more than that given in the report, which covered the period up to August 17.