Israeli troops killed at least 18 Palestinians along the Gaza border on Monday, health officials said, as thousands of demonstrators streamed toward the frontier as Israel prepared for the festive inauguration of a new US Embassy in contested Jerusalem. Monday’s march marked the biggest showdown yet in a weeks-long campaign against a decade-old blockade of the territory. A majority of Gazas 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. By midday, Israeli troops killed 18 Palestinians on Monday, including a 14-year-old boy and a man in a wheelchair, and some 500 protesters were injured, at least 200 by live bullets, health officials said. The man in the wheelchair had been pictured on social media using a slingshot. Protests intensified on the 70th anniversary of Israels founding, with loudspeakers on Gaza mosques urging Palestinians to join the "Great March of Return". Black smoke from tires burned by demonstrators rose into the air at the border. "Today is the big day when we will cross the fence and tell Israel and the world we will not accept being occupied forever," said Gaza science teacher Ali, who declined to give his last name. "Many may get martyred today, so many, but the world will hear our message. Occupation must end," he said. Israel dropped leaflets urging Palestinians to stay away from the fence. “Save your lives and work on building your futures,” it said. The latest casualties raised the Palestinian death toll to 61 since the protests began on March 30. No Israeli casualties have been reported. The Israeli military says its troops are defending the border and firing in accordance with the rules of engagement. "We are prepared to face the Hamas threats to disrupt the (embassy) festivities," Israeli Defence Minister Avigdor Lieberman tweeted. The killings have drawn international criticism, but the United States, which has infuriated the Palestinians and Arab powers by relocating its embassy to Jerusalem from Tel Aviv, has echoed Israel in accusing Gazas ruling Hamas movement of instigating violence, an allegation it denies. Later in the day, Israeli leaders and a US delegation including Treasury Secretary Steven Mnuchin and President Donald Trumps daughter and son-in-law, Ivanka Trump and Jared Kushner, were due to attend the opening of the embassy. "What a moving day for the people of Israel and the State of Israel," Israeli Prime Minister Benjamin Netanyahu said. Jason Greenblatt, Trumps Middle East peace envoy, said on Twitter that "taking the long-overdue step of moving our Embassy is not a departure from our strong commitment to facilitate a lasting peace deal. Rather, it is a necessary condition for it." But Palestinian Prime Minister Rami Hamdallah said Trumps recognition of Jerusalem as Israels capital in December and the relocation of the embassy were "blatant violations of international law". The Palestinians, who want their own future state with its capital in East Jerusalem, have been outraged by Trumps shift from previous administrations preference for keeping the US Embassy in Tel Aviv pending progress in peace efforts. Those talks have been frozen since 2014. Other international powers worry that the US move could also inflame Palestinian unrest in the occupied West Bank. 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 citys eastern half as the capital of a future state. Palestinian President Mahmoud Abbas cut ties with the Trump administration and declared it unfit to remain in its role as the sole mediator in peace talks. Saeb Erekat, a senior Abbas aide, blasted the Trump administration Monday, saying 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." Erekat said the Trump administration has "become part of the problem, not part of the solution." The protests are scheduled to culminate on Tuesday, the day Palestinians mourn as the "Nakba" or "Catastrophe" when, in 1948, hundreds of thousands of them were driven out of their homes or fled the fighting around Israels creation. "Choosing a tragic day in Palestinian history (to open the Jerusalem embassy) shows great insensibility and disrespect for the core principles of the peace process," Hamdallah wrote. Most countries say the status of Jerusalem - a sacred city to Jews, Muslins and Christians - should be determined in a final peace settlement and that moving their embassies now would prejudge any such deal. But Guatemala, which received support from Israel in its counter-insurgency campaigns in the 1980s, plans to open an embassy in Jerusalem on Wednesday. Its ambassador visited the new site, in an office building in the western part of the city, on Monday. Paraguay is to follow suit later this month. In response to the US decision, the Arab League will hold an extraordinary meeting to discuss the United State’s “illegal” move of embassy to Jerusalem, state news agency MENA reported on Monday, citing an Arab diplomat. MENA said the meeting will be held on Wednesday at the level of permanent representatives to the Arab League “to counter the illegal decision taken by the United States of America to transfer its embassy to Jerusalem”. US MOVE CONDEMNED In London, the British government said it had no plans to move its Israel embassy from Tel Aviv to Jerusalem, and said it disagreed with the US decision to do so. “The PM said in December when the announcement was first made that we disagree with the US decision to move its embassy to Jerusalem and recognize Jerusalem as the Israeli capital before a final status agreement. The British embassy to Israel is based in Tel Aviv and we have no plans to move it,” Prime Minister Theresa May’s spokesman told reporters on Monday. Also, Turkeys president condemned the US decision to move its Israel embassy to Jerusalem. In a statement published late Sunday, President Recep Tayyip Erdogan said the US disregarded "rights and justice," ignoring the international community. Erdogan says the move serves to "reward" the Israeli government despite it undermining efforts to resolve the decades-long conflict, while it "punished" Palestinians. "History and humanity will never forgive the injustices done to our Palestinian brothers," he added. The Russian government said it feared the embassy move would increase tensions across the Middle East.