The National Party leader is "comfortable" calling Russian leader Vladimir Putin a "war criminal", but the Prime Minister is refusing to say that explicitly.
Images of bodies strewn over the streets of the Ukrainian town of Bucha, which was until recently occupied by Russian forces, have shocked the world.
The United Nations High Commissioner for Human Rights Michelle Bachelet said the reports raise "serious and disturbing questions about possible war crimes", US President Joe Biden said it is a "war crime", while Ukrainian President Volodymyr Zelensky described it as a "genocide". Russia has denied all accusations.
Prime Minister Jacinda Ardern said it was "beyond reprehensible" and reiterated that New Zealand has already referred Russia's actions in Ukraine to the International Criminal Court, which is investigating.
"What we as an international community have seen are evidence of war crimes at the hands of Russia," Ardern said on Monday.
But Ardern refused to explicitly call Putin a "war criminal".
"When it comes to then going through the process of determining that that is indeed what has occurred, based on the evidence we've seen, that is something that we are supporting a formal process around.
"Ultimately, it is for the International Criminal Court to make that determination, but the evidence is there and New Zealand is supporting the prosecutors in gathering that evidence and making sure that Russia is held to account."
Pressed on why she isn't willing to join others in giving Putin that label, Ardern said: "I'm not willing for you to assume that I'm not".
"I'm not the judge in the International Criminal Court. We are supporting the International Criminal Court to make that determination, but every piece of evidence points to the fact that there are war crimes being committed by Russia in Ukraine at the hands of the President Vladimir Putin."
But National's Christopher Luxon, who previously called Putin "completely unhinged", went further.
"Officially, you have got to be prosecuted and convicted before you get labelled a criminal. But I would have to say to you that the evidence is pretty compelling, the evidence is there. I would be quite comfortable calling him a war criminal," Luxon said.
"The pictures we are all seeing are very alarming. I appreciate there is a process to go through before you get formally prosecuted, but I think we can see what is happening there and it is definitely war crimes."
Russia continues to have senior diplomats stationed in Wellington despite the current crisis. Since the invasion escalated in late February, National and others have been calling for the Russian Ambassador to New Zealand to be expelled.
Luxon repeated that call on Tuesday.
"That was one of the things we talked about from day one to say we think that sends a really strong signal. We said on day one that the time for diplomacy was over, it was finished and there was no intention for diplomatic resolution to this and you have continued to see that over the last month. From our point of view, we would have pulled our higher staff out of Moscow and we would have sent the Russian diplomat home."
Ardern was questioned on this on Monday. She said New Zealand has "used far more powerful tools to date whilst of course keeping on the table those other diplomatic options".
"You’ll see that very few countries have recalled their diplomatic representatives from Russia," she said.
"Between sanctions, tariffs, travel bans, export bans, providing military aid, providing equipment to Ukraine - when it comes to expelling ambassadors, that also means that you lose your representation in those countries. We haven’t ruled it out."
The Government has taken a number of steps in response to the invasion, including creating a new visa category for family members of Ukrainians in New Zealand, donating humanitarian aid, sending equipment to Ukraine and deploying intelligence officers to assist in Europe.
On Monday night, a new round of sanctions against Russian oligarchs was announced.
"New Zealand is appalled at reports over the weekend showing the targeted killing and abuse of civilians, as Russian troops withdraw from areas of Ukraine," Foreign Affairs Minister Nanaia Mahuta said.
"Through our sanctions, we are working with the international community to put real pressure on those supporting Putin and his regime, and send a clear message that this illegal invasion cannot continue, and that the brutality and inhumane acts from Russian troops cannot be tolerated."
Ukrainian-Kiwi lawyer Anastasiya Gutorova told AM on Tuesday that the Government could still go further with sanctions. Mahuta said more measures are expected in the coming weeks.
