Jacinda Ardern has condemned the "devastating, one-sided loss of life" in Gaza, as the United States opens its embassy to Israel in Jerusalem.

The prime minister said decision to move the embassy from Tel Aviv was a "step back" when it came to a peaceful, two-state resolution between Israelis and Palestinians.

The move came as a blow to Palestinians, who viewed part of Jerusalem as capital for a possible future state.

STUFF Prime Minister Jacinda Ardern told TVNZ she wasn't surprised by the violent clashes, as the US opens its embassy in Jerusalem.

Israeli soldiers have killed dozens of Palestinians - the death toll was 52 on Tuesday morning (NZT) - demonstrating along the border fence between Israel and the Gaza Strip. More than 2400 had been wounded in the bloodiest day in the enclave since the 2014 war with Israel, according to the Gaza Health Ministry.

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The violent backlash did not come as a surprise, Ardern said.

An estimated 35,000 Palestinians gathered on the edges of Gaza as the US Embassy opened in Jerusalem, fanning out along the fence in the largest demonstrations yet.

At a gathering point east of Gaza City, organisers urged demonstrators to burst through the fence, telling them Israeli soldiers were fleeing their positions, even as they were reinforcing them.

At the barrier, young men threw stones and tried to launch kites carrying flames in hopes of burning crops on the other side. Most of the demonstrators, though, were peaceful, protesting the loss of their homes and villages and the embassy move.

EVAN VUCCI/AP US President Donald Trump's December announcement recognising Jerusalem as Israel's capital and ordering that the embassy be moved broke decades of US policy.

"This is a hotly contested issue within that peace process, and as we've seen the results of the protests along the border of Gaza have been devastating," Ardern said.

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

The Ministry of Foreign Affairs had raised concerns, on behalf of the Government, directly with the Israeli ambassador in the past 10 days, and would speak with the ambassador again about the latest conflict within the next two days, Ardern said.

JASON DORDAY/STUFF "As predicted the opening of Donald Trump's confrontational Embassy in Jerusalem has fanned flames of conflict and death," Green Party co-leader Marama Davidson says.

Last year, US President Donald Trump said the US Embassy in Israel would be moving from Tel Aviv to Jerusalem, in an effort to recognise Jerusalem as the capital of Israel. The opening had been timed to coincide with Israel's Independence Day.

Following the announcement in December, New Zealand was among 128 nations voting for a UN resolution condemning the United States for recognising Jerusalem as the capital of Israel.

The US and Israel resoundingly lost the non-binding general assembly vote 128-9. The resolution didn't name the US explicitly but expressed "deep regret" at any decision to recognise Jerusalem as Israel's capital - which US President Trump decided to do on December 6, 2017.

REXINE HAWES/STUFF Meanwhile, National Party leader Simon Bridges says a case can be made for the US moving its embassy to Jerusalem.

"We made our voice heard at that time - that it was our view that this did not bring us closer towards that peaceful resolution; that two-state solution, which New Zealand has long-supported," Ardern said about the UN vote.

"It certainly doesn't sit within the framework of a two-state solution. It is a heavily contested and disputed part of any future settlement, and I think that has come to fruition.

"This has taken us a step back, rather than a step forward... Certainly we feel no closer today than we did six months ago."

Ardern said the Government had not spoken directly to the US, or US Ambassador, following the deaths.

TRUMP'S EMBASSY 'FANS FLAMES OF DEATH'

The Green Party also said it "strongly condemned the slaughter perpetrated by the Israeli armed forces".

Green Party co-leader Marama Davidson called the deaths murder, adding "this is the second deadly massacre of protesters perpetrated by the Israeli armed forces this year and is the deadliest onslaught in Gaza since 2014".

"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 had acted as a flash point in the conflict, she said.

"Jerusalem is an internationally recognised disputed territory, and the fair division of it will be a component of any enduring peace deal. The United States setting up an Embassy there purposefully undermines the Palestinian position and makes peace less likely.

"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."

Meanwhile, National leader Simon Bridges said the US had "stood on its rights" and in doing so, had made a case for the embassy, but it had led to an unsafe situation.

"You can make the case for what America has done here. But ultimately, it's hard to argue this has made things more safe; it's made things less safe...

"Let's call for restraint on both sides... but there's no doubt the US Embassy in Jerusalem has inflamed things," Bridges said.