Prime Minister Jacinda Ardern says the deaths of Palestinians in Gaza at a protest were "a devastating, one-sided loss of life" and showed concerns about the United States' decision to relocate its embassy were warranted.

More than 50 Palestinians were killed and 2400 wounded by Israeli soldiers during protests against the US opening its new embassy in Jerusalem, moving it from Te Aviv.

The Ministry of Foreign Affairs had repeated the Government's concerns about the move of the US Embassy directly with Israel's Ambassador in the weeks before it took place.

Ardern said New Zealand had long supported a two-state solution and warned that the US move would be a backwards step. "And it has."

"You will recall at the time the United States announced they would be moving their representation to Jerusalem we stated at that time strongly that we did not believe that would take us closer to peace and it hasn't," Ardern said.

"As we've seen, the results of the protests along the border at Gaza has been devastating.

"It is the right of any nation to defend their border, but this is a devastating, one-sided loss of life. We would condemn the violence that has occurred and it's plain to see the effects of this decision and the ramifications are wide reaching."

New Zealand had not yet made any direct representations to the United States about the recent events, but had made its views of US President Donald Trump's decision to move the embassy to Jerusalem clear when that decision was made.

National Party leader Simon Bridges said there was no doubt the move of the US Embassy to Jerusalem had inflamed matters.

"I think you can make the case for what America has done here, but ultimately it's hard to argue that this has made things more safe. It's certainly made things less safe and it's worried, troubling to see what's happening at the moment."

Asked if New Zealand should be raising a protest directly with the US, he said "you can, if you stand on your rights, make the case for the US Embassy there, but the other side of it is it's inflammatory".

He said there needed to be restraint and proportionality on all sides.

Green Party co-leader Marama Davidson, who took part in activists' effort to break the blockade of Gaza in 2016, put the blame squarely in the hands of the US, saying it had provided the Israeli Government with an excuse "to justify their massacre of Palestinians".

"As predicted the opening of Donald Trump's confrontational Embassy in Jerusalem has fanned flames of conflict and death.

"Rather than being a step towards peace the embassy opening has acted as a flash point in the conflict and has been used by the Israeli Government to justify their massacre of Palestinians."

She said Jerusalem was an internationally recognised disputed territory and a "fair division" was the only hope of peace.

"This slaughter is all the evidence we need that Trump's move makes peace less likely and makes life for those living in Gaza more dangerous."