GAZA CITY, Gaza Strip (AP) — Israeli soldiers shot and killed at least 52 Palestinians during mass protests along the Gaza border on Monday. It was the deadliest day there since a devastating 2014 cross-border war and cast a shadow over Israel’s festive inauguration of the new U.S. Embassy in contested Jerusalem.

In a show of anger fueled by the embassy move, protesters set tires on fire, sending plumes of black smoke into the air, and hurled firebombs and stones toward Israeli troops across the border. Later on Monday, Israeli forces fired from tanks, sending protesters fleeing to take cover.

The military said its troops came under fire in some areas, and said protesters tried to break through the border fence. It said troops shot and killed three Palestinians trying to plant a bomb.

President Donald Trump said in a video message played at the embassy inauguration — which took place just 70 kilometers (45 kilometers) from the bloodshed on the Gaza border — that he remains committed to “facilitating a lasting peace agreement” between Israelis and Palestinians.

“A great day for Israel!” Trump tweeted earlier Monday.

However, Monday’s steadily climbing death toll and wall-to-wall condemnation of the embassy move by the Arab world raised new doubts about Trump’s ambitions to broker what he once said would be the Mideast “deal of the century.”

By late afternoon, at least 52 Palestinians, including five minors, were killed, the Gaza Health Ministry said. One of the minors was identified as a girl.

The ministry said 1,204 Palestinians were shot and wounded, including 116 who were in serious or critical condition.

The statement says about 1,200 others suffered other types of injuries, including from tear gas.

At the embassy ceremony in Jerusalem, Trump son-in-law and chief Mideast adviser Jared Kushner placed the blame on the Gaza protesters.

“As we have seen from the protests of the last month and even today those provoking violence are part of the problem and not part of the solution,” he said.

Kushner and Trump daughter Ivanka led a high-powered American delegation that also included the treasury secretary and four Republican senators.

The new embassy will temporarily operate from an existing U.S. consulate, until a decision has been made on a permanent location.

In Gaza, the Hamas-led protest was meant to be the biggest yet in a weeks-long campaign against a decade-old blockade of the territory. The Israeli military estimated a turnout of about 40,000, saying this fell short of what Hamas had hoped for.

The march was also directed at the inauguration of the embassy.

Moving the embassy from Tel Aviv to Jerusalem — a key Trump campaign promise — infuriated the Palestinians, who seek east Jerusalem as a future capital.

Monday marked the biggest showdown in years between Israel’s military and Gaza’s Hamas rulers along the volatile border. The sides have largely observed a cease-fire since the 2014 war — their third in a decade.

The protest was the culmination of a campaign, led by Hamas and fueled by despair among Gaza’s 2 million people, to break the blockade of the territory imposed by Israel and Egypt after Hamas seized control of Gaza in 2007. Since weekly border marches began in late March, 85 Palestinian protesters have been killed and more than 2,500 wounded by Israeli army fire. Hamas said four members, including three security men, were among the dead Monday.

Ismail Radwan, a senior Hamas figure, said the mass border protests against Israel will continue “until the rights of the Palestinian people are achieved.”

“Moving the U.S. Embassy to Jerusalem will be a disaster for the American administration and a black day in the history of the American people because they are partners with the occupation and its aggression against the Palestinian people,” he added.

Throughout the day, sirens wailed as the wounded were carried to nearby ambulances. Groups of young activists repeatedly approached the fence, but were quickly scattered by gunfire and tear gas.

Lt. Col. Jonathan Conricus, an Israeli military spokesman, said the army had set up additional “layers” of security in and around communities near the border to defend Israeli civilians. He said there already had been several “significant attempts” to break through the fence. The army said aircraft targeted a Hamas post in northern Gaza after Israeli troops came under fire.

The timing of Monday’s events was deeply symbolic to Israel and the Palestinians.

The U.S. said it chose the date to coincide with the 70th anniversary of Israel’s establishment.

But it also marks the anniversary of what Palestinians call their “nakba,” or catastrophe, a reference to the uprooting of hundreds of thousands who fled or were expelled during the 1948 war surrounding Israel’s creation.

A majority of Gaza’s 2 million people are descendants of refugees, and the protests have been billed as the “Great March of Return” to long-lost homes in what is now Israel.

Protester Mohammed Hamami, a 40-year-old civil servant, attended the march with his mother and five children. “Today we are here to send a message to Israel and its allies that we will never give up on our land,” he said.

Clouds of black smoke from burning tires rose into the air. Protesters have used the thick smoke as cover against Israeli snipers perched on high sand berms on the other side of the border. The army accuses Hamas of using the protests as cover to plan or carry out attacks.

Israel captured east Jerusalem in the 1967 Mideast war and annexed it in a move not recognized by the international community. The Palestinians seek the city’s eastern half as the capital of a future state.

Palestinian President Mahmoud Abbas cut ties with the Trump administration and declared it unfit to mediate peace talks.

Saeb Erekat, a senior Abbas aide, said Monday that Trump had violated a promise to hold off on moving the embassy to give peace talks a chance and that his administration is “based on lies.”

Israeli Prime Minister Benjamin Netanyahu has repeatedly praised Trump’s decision to upend decades of U.S. policy by recognizing Jerusalem as Israel’s capital.

Although Trump has said his declaration does not set the final borders of the city, it is seen by both Israel and the Palestinians as taking Israel’s side in the most sensitive issue in their conflict.

Only two countries, Guatemala and Paraguay, have said they will follow suit. Most of the world maintains embassies in Tel Aviv, saying the Jerusalem issue must first be resolved.

A Palestinian woman walks through black smoke from burning tires during a protest on the Gaza Strip’s border with Israel, Monday, May 14, 2018. Thousands of Palestinians are protesting near Gaza’s border with Israel, as Israel prepared for the festive inauguration of a new U.S. Embassy in contested Jerusalem. (AP Photo/Khalil Hamra)