Russia-Ukraine war: Vladimir Putin, 'just like the protesters in front of Parliament', needs to go home - Helen Clark

Intelligence indicates Ukraine is facing an uphill battle, former New Zealand Prime Minister Helen Clark says, as Ukrainians face the terrifying force of a deadly Russian onslaught.

Russian troops began attacking Ukraine forces and military bases in the early hours of Thursday (local time), resulting in the UK and the US unleashing new rounds of sanctions - potentially shutting Russia out of the world's economy.

Clark, a former UN administrator, says Russian President Vladimir Putin wants Ukraine to be a "compliant state" and not part of the North Atlantic Treaty Organization (NATO) - a military alliance between the US, Canada and 28 European countries including the UK and France. 

Putin has manufactured excuses for why he needs to invade Ukraine, Clark told AM.

"Russia will seek to cut off the bulk of the Ukrainian army which is on the eastern line of [the] conflict with the separatists," Clark said. "Unless that army were to strategically retreat quite quickly, it would not be able to mount a defence of Kyiv (Ukraine capital) and other major centres."

Clark said Putin's excuses for the invasion weren't "holding any water" with the West.

"He could go all the way to try to occupy the country. Of course, he said… 'we're not going to occupy Ukraine' but just about everything else that Russia has said has proved to be incorrect."

Clark said Putin could trap the Ukrainian government in Kyiv.

"The news that we're hearing… is showing some pretty worrying reports from around Kyiv itself with the fighting over the airport."

Clark said the Kremlin was, in a sense, trying to recreate the Soviet Union

She said should Putin seize control of Ukraine, there would be concerns over Moldova just south of Ukraine - also a former Soviet state.

"There's sort of a gameplan here and this is, without doubt, the boldest and most ruthless of these moves to recreate the old order."

Asked what her message to Putin was, Clark said: "Pretty much like that to the protesters in front of Parliament - 'go home.'" 

Earlier on Friday morning (NZ time), US President Joe Biden vowed to make Russia pay dearly for invading Ukraine.

While the latest round of harsh new sanctions targeted Russia's economy, they didn't include a direct sanction on Putin himself.

But Biden said the latest sanctions would be enough to hit Putin where it hurts.

"Putin is the aggressor. Putin chose this war," Biden told reporters at the White House. 

"Now he and his country will bear the consequences.

"Putin's aggression against Ukraine will end up costing Russia dearly."