Reports of a Russian pullback from Ukraine were “unconvincing and unconfirmed”, Prime Minister Scott Morrison says.

Mr Morrison told parliament on Wednesday cyber attacks on Ukraine ran counter to reports that Russia was about to engage in a pullback.

“Russia must unconditionally withdraw,” he told parliament.

“If Russia attacks Ukraine, it will be met with overwhelming international condemnation. The world will not forget that Russia chose needless death and destruction.”

Earlier, a senior foreign affairs official said Australia remained cautiously optimistic about reports of Russian troops withdrawing from the Ukrainian border.

But foreign affairs department deputy secretary Katrina Cooper told a Senate committee there was deep concern about the situation, as US President Joe Biden said there are more than 150,000 troops encircling Ukraine and Belarus and “an invasion remains distinctly possible”.

“We’re hearing suggestions that a diplomatic off-ramp is still possible,” she said.

“There’s grounds for very cautious optimism in terms of what we’ve seen overnight. It’s an encouraging sign we are hearing (but) those reports are coming out of Russia — we do need to drill down a little bit into that.”

Ukraine chargé d`affaires Volodymyr Shalkivski says banks and their websites were targeted by cyber attacks and remain down.

“But there is no panic on the ground. We are prepared for any case scenario,” he told the ABC on Wednesday.

Australia’s cyber affairs ambassador Tobias Feakin said detailed discussions regarding cyber cooperation with Ukrainian counterparts are “well progressed”.

Ms Cooper also flagged that while Australia’s sanctions regime was quite broad, the department was actively considering strengthening its autonomous sanctions regime subject to the government’s approval.

Mr Shalkivski said Ukraine appreciated the strong stance Australia had taken against Russian aggression and was grateful for the assistance and defence capabilities of Western partners.

“We are part of the free world, free and liberal democracies, and it is really important for us to feel such support,” he said.

“This is our country, our land. We will defend it with all military and technical means that we have in our disposal.”

Labor senator Kristina Keneally said officials had been too “passive” with Ukrainian support, with offers for help not being backed up with action.

Foreign Minister Marise Payne vehemently denied any hesitation or passivity on behalf of Australia.

“We are ready to move when those countries move,” Senator Payne said regarding Russian sanctions.

“It’s not the case in any way, shape or form you could characterise the government’s response as passive.”

The Australian embassy and three diplomatic staff were co-located with the Canadian embassy in Ukraine’s capital Kyiv, but both have now moved to Lviv, and remain operational and continue to co-locate.

Senate estimates was told 186 Australians in Ukraine have registered with the Department of Foreign Affairs and Trade, and a large number had already left.

– AAP