*More than 2,700 Palestinians wounded
*US no longer a mediator, says Abbas

Israeli troops shot dead dozens of Palestinian protesters on the Gaza border on Monday as the United States opened its embassy to Israel in Jerusalem, a move that has fueled Palestinian anger and drawn foreign criticism that it undermines peace efforts.

It was the bloodiest single day for Palestinians since the Gaza conflict in 2014. Palestinian Health Ministry officials said 55 protesters were killed and 2,700 injured either by live gunfire, tear gas or other means.

The bloodshed drew calls for restraint from some countries, including France and Britain, and stronger criticism from others, with Turkey calling it "a massacre".

The White House declined to join in urging Israel to exercise restraint and pinned the blame squarely on Gaza's ruling Hamas group - backing Prime Minister Benjamin Netanyahu, who described the Israeli military's actions as self-defence of his country's borders.

The dead included eight children under the age of 16, according to the Palestinian envoy to the United Nations.

The embassy inauguration nonetheless went on as planned, attended by a Washington delegation that included US President Donald Trump's daughter Ivanka and her husband Jared Kushner, both White House aides.

Ivanka Trump helped declare the new embassy open and a plaque and seal were unveiled before the 800 guests at the ceremony.

Trump addressed the ceremony by video.

"Our greatest hope is for peace," he said despite the Palestinian anger the move has provoked.

"The United States remains fully committed to facilitating a lasting peace agreement."

Israeli Prime Minister Benjamin Netanyahu told Trump in his address that "by recognising history you have made history."

Along the Gaza border, crowds built throughout the day in the Palestinian enclave less than 100 km away from Jerusalem and sealed off from Israel by a blockade.

Israel's military said 40,000 Palestinians had taken part in the protests and clashes.

"The rioters are hurling firebombs and explosive devices at the security fence and at (Israeli) troops and are burning tyres, throwing rocks and launching flaming objects with the intention of igniting fires in Israeli territory and harming (Israeli) troops."

The military also said one of its fighter jets had struck five targets at a Hamas training facility in Gaza.

Earlier, a military plane and tank targeted two other Hamas posts in response to what it said was fire toward its forces by Hamas.

Palestinian president Mahmoud Abbas accused Israel of "massacres," while Amnesty International called the violence an "abhorrent violation" of human rights. Human Rights Watch denounced a "bloodbath."

EU foreign policy chief Federica Mogherini said "we expect all to act with utmost restraint to avoid further loss of life," while British Prime Minister Theresa May's spokesman urged "calm and restraint".

Netanyahu defended the use of force, saying "every country has the obligation to defend its borders."

The inauguration followed Trump's December 6 recognition of the disputed city as Israel's capital.

The ceremony took place at what until now had been a US consulate building in Jerusalem.

Abbas said the new embassy was tantamount to "a new American settler outpost" in Jerusalem and that the United States "is no longer a mediator in the Middle East."

Police and the Israeli military deployed massively.

Around 1,000 police officers were positioned around the embassy, while Israel's army said it almost doubled the number of troops surrounding Gaza and in the occupied West Bank.

Israel occupied the West Bank and east Jerusalem in 1967 and later annexed east Jerusalem in a move never recognised by the international community.

Beyond the disputed nature of Jerusalem, the date of the embassy move was also key.

May 14 marks the 70th anniversary of the founding of Israel.

Today, Palestinians mark the "Nakba", or catastrophe, commemorating the more than 700,000 Palestinians who fled or were expelled from their homes in the 1948 war surrounding Israel's creation.

Palestinian protests are also planned for today.

There had already been weeks of protests and clashes along the Gaza border, with 106 Palestinians killed by Israeli fire there since March 30.

No Israelis have been killed and the military has faced criticism over the use of live fire.

Jerusalem's status is perhaps the thorniest issue in the Israeli-Palestinian conflict.

Israel considers the entire city its capital, while the Palestinians see east Jerusalem as the capital of their future state.

In the decades since 1967, international consensus has been that the city's status must be negotiated between the two sides, but Trump broke with that to global outrage.

He has argued that it helps make peace possible by taking Jerusalem "off the table", but many have pointed out he has not announced any concessions in return from Israel.

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