Vladimir Putin has 'sick' fantasy to restore the Soviet Union: Ukrainian diplomat Volodymyr Shalkivskyi

Ukrainian head of mission to Australia Volodymyr Shalkivskyi on Thursday also warned Russia and Belarus have designs on the Baltic region, potentially drawing NATO into a full-blown war.

Speaking to the National Press Club, Mr Shalkivskyi said by removing dissenting voices in the Kremlin, Russian President Vladimir Putin had constructed a fantasy in which Ukrainians would welcome his troops.

"This is about the sick idea of a dictator to restore the Soviet Union, something that constitutes the biggest strategy for him personally. And he believed that this is the perfect time," he said.

"Mr Putin truly believed that people would greet [Russian troops] with flowers, but the fact is [they] were greeted with Molotov cocktails."

The Russian invasion, which seemed to expect a lightning advance through Ukraine, has stalled after fierce resistance from Ukrainians.

Mr Shalkivskyi said the symbolism of Ukrainian President Volodymyr Zelensky staying in Kyiv to fight was important in mobilising a response that has surprised the Kremlin.

He revealed his 73-year-old mother had remained in the Ukrainian capital, asking for Molotov cocktail recipes to fight the invading forces.

"As my father told me: two nights in a bomb shelter is enough to completely change any pro-Russian sentiment that you have in your heart," he said.

Russian bombardments have targeted residential areas, also killing Ukrainian civilians on roads used to flee the capital.

Moscow's stalled advance, and its history of razing civilian areas in Chechnya and Syria, has sparked fears it is preparing to escalate its offensive.

"If it is continues ... to my mind it's genocide. If it is not genocide, what's the definition of genocide?" Mr Shalkivskyi said.

NATO has resisted calls from Kyiv to implement a no-fly zone over Ukraine, which it argued would prompt an all-out war between nuclear powers.

But Europe's eastern flank is already bracing for the worst. The three Baltic states - Estonia, Latvia, and Lithuania - escaped Soviet occupation in 1991, and have since joined NATO and the European Union.

While the Kremlin has threatened Finland and Sweden with consequences if they join the military pact, an attack on the Baltics would trigger a response from the entirety of NATO.

An estimated one million ethnic Russians live in the Baltic states, and Mr Putin's claim to be protecting Russians in Ukraine has prompted concern the region is in his sights.

Mr Shalkivskyi warned the international community not to be complacent, after Belarussian President Alexander Lukashenko - Putin's sole military ally - pledged to have his own ports in the Baltic Sea.

"It is a clear sign that this is the long-term strategy," he said.

Reports in the US suggest the Pentagon is preparing to fund a long-term insurgency in Ukraine, with former Secretary of State Hillary Clinton citing Afghanistan as a model to suck in Russian resources.

Mr Shalkivskyi would not be drawn on whether Kyiv's western allies saw a quagmire in Ukraine as an acceptable strategy, but insisted it is prepared for a "long-term war".

While he said there is no indication Moscow is preparing to back off in the short-term, he questioned its ability to remain for years, having already sustained significant losses in the first 13 days of the conflict.

The federal government has committed $70m in "lethal and non-lethal" aid to Ukraine, with military support to be coordinated by NATO.

But Russia's ambassador to Australia Alexey Pavlovsky remains in Canberra for now. Mr Shalkivskyi said he understood Australia's position, but warned "Mr Putin respects only strength".

He called for Mr Pavlovsky to be booted out, saying combating Russia required "maximum pressure" - combining military force, humanitarian aid, and isolating Moscow diplomatically.

"Every government needs to have a line of communication, but I'm not in the position to be diplomatically polite," he said.

"Having your parents in bomb shelters makes you more decisive."

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Kyiv has established a foreign legion and urged foreigners to join the fight, something Prime Minister Scott Morrison warned could be a legally fraught "suicide mission".

Mr Shalkivskyi confirmed Australians have expressed an interest in travelling to the warzone, but was not clear on whether any had. He warned prospective fighters to clearly understand the legal ramifications before boarding a plane.

"We will welcome such assistance to fight for our freedom, and we as an embassy will facilitate it," he said.

"But I always stress that we do not want you guys to get in trouble on your way back home."