Russia's Embassy in New Zealand has used its Facebook page to say that alleged war crimes uncovered in parts of Ukraine are a "hoax".

New Zealand's Government and Opposition have both aligned with Ukrainian accounts of atrocities, with the Prime Minister saying the reported crimes were "beyond reprehensible".

"Russia must answer to the world for what they've done," Ardern said. This week, Ardern faced renewed calls to expel Russia's ambassador.

On Monday, the Russian Embassy's Facebook page alleged that all "photos and videos published by the Kiev regime allegedly testifying to some "crimes" committed by Russian servicemen in Bucha, Kiev region are just another provocation".

The post went on to allege that "not a single local resident has suffered from any violent action" in Bucha while it was under Russian occupation.

Multiple foreign media outlets have subsequently visited Bucha and recorded evidence of what appear to be civilians who were murdered by Russian troops. They have photographed bodies dumped on the side of the road, hands tied, apparently executed by Russian troops. Accounts of survivors have alleged Ukrainian women were raped by Russian troops.

One post went into graphic detail in an attempt to discredit Ukraine's account of events. The post said the bodies were not sufficiently stiffened, and "have no typical cadaver stains, and the wounds contain unconsumed blood", and must therefore be fake.

The embassy made two subsequent posts. One linked to a website which alleged "people's minds are manipulated" by fake images, another was a video of Russia's Permanent Representative to the United Nations Ambassador Vassily Nebenzia denying the allegations of war crimes.

"The Russian military has [done] nothing of what it is accused of," Nebenzia said in the post.

"We have evidence that proves this point and we plan to present it to the Security Council as soon as possible," he said.

The Government is convinced Russia needs to answer to the allegations made against it.

Alongside other nations, New Zealand has referred the case to the International Criminal Court.

Ardern has so far refused to expel Russia's ambassador to New Zealand. On Monday, she appeared open to the idea that she might do so in the future.

"New Zealand has had this raft of options in front of us—as has every other country—around diplomatic tools," Ardern said.

"To be honest, my view is that we have used far more powerful tools to date whilst of course keeping on the table those other diplomatic options," she said.

She said that expelling the ambassador would mean New Zealand also losing representation in Russia, which could pose problems.

National leader Christopher Luxon repeated his call to expel Russia's ambassador.

"That was one of the things we talked about from day one to say we think that sends a really strong signal," Luxon said.

"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," he said.

The Russian Embassy was approached for comment.