New Zealand has waded into an almighty and dangerous scrap between Australia and China - taking the side of our closest mates, the Aussies.

Prime Minister Jacinda Ardern says the Government has directly raised concerns with China over a graphic fake tweet showing an Australian soldier, and National has gone even further calling China immature, incendiary and abhorrent.

"New Zealand doesn't support disinformation that has the potential to be inflammatory," Foreign Affairs Minister Nanaia Mahuta said in response on Tuesday.

The 'inflammatory disinformation' she's referring to is a tweet from China's foreign ministry spokesman Lijian Zhao. The graphic image shows an Australian soldier holding a knife to the neck of a child.

New Zealand has gone in to bat for Australia directly raising concerns with China.

"In keeping with our principled position where images like that are used we will raise those concerns and we'll do it directly," Ardern told reporters.

The doctored image and tweet refer to alleged war crimes by Australian soldiers - that elite SAS troops executed 39 civilians in Afghanistan.

The Chinese government has officially doubled down saying Australia should be ashamed.

• New Zealand has raised concerns with China over falsified image of Australian soldier
• Leaked documents show China's data fumblings in early stages of pandemic
• New Zealand raises concern directly with China over fake Australian soldier image
• Australia demands apology from China after fake image posted on social media

"The Australian side reacted so strongly to my colleague's personal tweet, does it mean to show that it is reasonable for some Australian soldiers to coldly kill the innocent people in Afghanistan and it is not unreasonable for anyone to condemn this cold crime?" said Chinese foreign ministry spokeswoman Hua Chunying.

It was a direct return fire at Australian Prime Minister Scott Morrison who said Beijing should be "utterly ashamed" for sharing the "repugnant" image.

"We have raised concerns," Ardern said. "This is an image that wasn't factual, it wasn't correct."

Ardern chose her words carefully while National went all in, with leader Judith Collins agreeing with Morrison's outrage.

"If it's a false thing, absolutely," Collins said, when asked if she agreed that the tweet was repugnant. "I haven't seen the tweet but it sounds abhorrent."

National's foreign spokesperson Gerry Brownlee didn't hold back.

"It was inappropriate to doctor the photograph of the Australia military person and I think it doesn't really befit a country of China's stature to be doing that," he told reporters.

"Incendiary is how I'd describe it," Brownlee added. "Fairly immature in terms of international diplomacy."

The Prime Minister has defended raising concerns with China over its fake tweet but not raising concerns with Australia over the alleged killing of Afghan civilians, saying when it comes to behaviour at war it's for each country to take responsibility and action.