The prime minister says it is difficult to assess the reliability of information the government has about the whereabouts of the body of New Zealand soldier Corporal Dominic Abelen, who died fighting Russian forces while on leave without pay.
Jacinda Ardern told Morning Report she was limited in what she could reveal, given considerations of Corporal Abelen's family's privacy, as well as security arrangements and "the uncertainty of the information".
"I may well, yes, be aware of a bit more detail than that's in the public domain but there's good reason for that," she said.
"This is a situation where, you can imagine, there's first the privacy of the family and then there's the security situation."
She would not be drawn on whether she had information to suggest that Abelen's body was in Russian hands.
"This is an area where both the information is uncertain and also, I'm just not in a position to provide it ... and this is out of huge respect for the family as well."
Ardern said New Zealand did not have diplomatic staff on the ground in Ukraine, which made it difficult to be certain of the information being received.
"We're staying in close contact with the family, doing what we can, but there's obviously a good reason why we do advise that New Zealanders not to travel into the area, because we aren't able to support on the ground."
All information the government had received was being shared with Abelen's family, Ardern said, including where there was uncertainty about the information.
"As you can imagine, it's a war zone," she said.
"So when we hand that over - what we know - it's caveated, that it may not - we're unable to verify it."
On Friday, a spokesperson for Ardern said it the government did not know where Abelen's body was, or if it would be possible to bring him home.
Ardern today reiterated that the government was "very constrained" in what it could do in the current circumstances.
"It's very difficult for us to do much at this present point in time; that does not mean however that we're not seeking as much as information as possible."
She said there were "no foreign nationals there on the ground fighting on behalf of their governments".
"So we are doing what we can to support the family, but at this time, we are very constrained."
Govt 'not aware' of any NZDF staff in Ukraine
The New Zealand Defence Force (NZDF) still cannot rule out the possibility more of its soldiers are fighting in Ukraine.
On Friday, it said it had been trying to contact all 94 of its staff on unpaid leave.
It said no staff had permission to enter Ukraine and it was not aware of any of its soldiers serving there.
Three days on, it could not say how many had been contacted or how many were overseas.
Ardern said the 94 NZDF individuals on upaid leave were split across the army, the navy and the airforce.
"We are not aware of any that've gone into Ukraine, because of course, if you're on leave without pay, the expectation is that you not be in Ukraine; that's one of the expectations of the New Zealand Defence Force."
However she said the NZDF had made clear that it "may well not be aware" if someone chose to go to Ukraine without advising it.
NZDF said it was doing what it could to reach out to personnel, but the process relied on them being forthcoming with accurate information.