Foreign Affairs Minister Nanaia Mahuta says evidence is "piling up" of war crimes by Russia in Ukraine, but would not go so far as labelling President Vladimir Putin a war criminal.
Overnight, New Zealand added a further 36 individuals to its Russia sanctions list.
The sanctions ban those listed from travelling or moving assets here, or using New Zealand's financial systems to hide from sanctions imposed elsewhere.
On Monday, Prime Minister Jacinda Ardern said there was evidence of war crimes by Russia in Ukraine, but she stopped short of calling President Vladimir Putin a war criminal.
Ardern said the government isn't ready yet to expel the Russian ambassador from New Zealand.
Foreign Affairs Minister Nanaia Mahuta told Morning Report expelling the ambassador is an option, but New Zealand is currently keeping diplomatic options open.
"We've called the ambassador in a number of times. Moscow is under no shadow of a doubt about where New Zealand stands on this war," she said.
Mahuta said there was enough evidence for the international criminal court to make an assessment of events in Ukraine.
"Putin's war is actually creating not only significant war crimes and evidence of that but actually there's no word to describe the abhorrent images and descriptions of civilians that have recently been decimated at Bucha.
"There is, again, no shadow of a doubt, based on the images and descriptions that people are seeing reported from Ukraine, that there is enough there for the International Criminal Court to make its assessment and we support them to do that."
She said the court's legal threshold needed to be passed before words like genocide could be applied.
Ukrainian officials are in the process of recovering hundreds of bodies of civilians they say were raped, tortured, and then slaughtered, on the outskirts of the capital Kyiv.
King's College London lecturer Dr Maria Varaki, who is also co-director of the War Crimes Research Group, told Morning Report the international community is working closely to hold Russia accountable for these atrocities.
"The horrific images and reports we have from the ground from Bucha but actually from other cities in Ukraine they raise, as the UN Human Rights Comissioner says, serious questions about possible war crimes."
However, Varaki said any verdict was likely to be a long time away due to the nature of international law.
"We are not going to have an immediate result because we are talking about very difficult and complex situations.
"It's an extremely challenging task to complete a reliable investigation when you have an ongoing conflict, something that we experience in Ukraine," she said.
Varaki said a reliable and independent investigation on behalf of the prosecutor was needed to combat Russia's claims that reported atrocities were the result of propaganda and fake news.
The government has approved sanctions on a further 36 Russian oligarchs or people with close ties to the Russian regime or the Russian President himself.
None of them are in New Zealand, but one notable addition is billionaire Roman Abramovich - the former Chelsea FC owner who suffered symptoms of suspected poisoning at talks in Kyiv last month.
National Party spokesperson for Foreign Affairs Gerry Brownlee Photo: RNZ / Dom Thomas
National Party spokesperson for Foreign Affairs Gerry Brownlee says the process for who's sanctioned, and who hasn't made the list, could be clearer.
"There is for example the connection around a steel company and if that steel company was providing steel or the manufacture of Russian military equipment, that's not a direct connection to Vladimir Putin but that's a heck of a connection to the poor people on the end of those weapons," Brownlee said.
He also questioned the government's decision not to expel the Russian ambassador to New Zealand.
Brownlee said consular services could remain in both countries but he challenged the need for higher level diplomatic representation.
"At the moment, the government has said that all diplomatic connection with Russia is cut off so what do we need this guy here for and why do we need our ambassador there?
"Symbolically, I think it's quite significant that we have Vladimir Putin's representative, his mouthpiece, here in Wellington."
With the war in Ukraine now over a month-long, Brownlee said New Zealanders who had decided to stay in Russia had made a choice.
"I hate to be harsh about that but we can't be half-in-half-out here," he said.
Brownlee said the government's diplomatic response needed to show New Zealand did not tolerate Russia's actions in any capacity.
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