At least 41 Palestinians were shot dead by Israeli forces as thousands protested against the inauguration of the US embassy in Jerusalem.
More than 1,000 people were wounded, the Gaza health ministry said, as Israel deployed two extra brigades to join at least 100 snipers and other troops along the frontier with the strip.
Protesters burnt tyres, sending huge plumes of black smoke to the sky, and threw stones and brandished knives at Israeli soldiers, including snipers perched on earthen berms.
US President Donald Trump recently recognised Jerusalem as the capital of Israel. An official opening ceremony for the movement of the embassy to Jerusalem from Tel Aviv is currently underway, with Israeli Prime Minister Benjamin Netanyahu and several top officials from the US on the ground.
Among them are Jared Kushner, an in-law of Trump, and his wife, Ivanka, who is Trump’s daughter.
The Israeli air force said it carried out three strikes at “military posts” in northern Gaza controlled by Hamas, the militant group that controls the impoverished hemmed-in strip.
Monday’s death toll was the biggest in a single day since the Hamas-led protests began in March in the build-up to this week’s 70th anniversary of the founding of the state of Israel.
The Israeli military said those who were shot posed immediate threats to its security.
In a recorded video clip with biblical references, Trump said: “Israel is a sovereign nation, with the right like every other sovereign nation to determine it own capital”.
“The plain reality is that Israel’s capital is Jerusalem. Today we follow through on this recognition and open our embassy on this sacred land of Jerusalem.”
“We are in Jerusalem and we are here to stay,” the Israeli leader said. “What a glorious day — remember this day. This is history.”
Trump’s decision this year to recognise Jerusalem as the capital of Israel reversed decades of US policy and drew criticism from Europe and Washington’s main Arab allies.
The status of the holy city is one of the most contested issues in the Israeli-Palestinian peace process, and critics of Mr Trump’s say it undermines the US’s role as the Middle East’s broker and dashes hopes of a two-state solution.