Gaza massacre: Israel kills dozens of Palestinian 'return' protesters
The death toll, which is expected to rise, makes it the deadliest day in the Israeli-Palestinian conflict since the 2014 Gaza war.
The 52, including a 14-year-old, were killed by Israeli snipers positioned along the border. Israel's military nearly doubled its deployment of troops around Gaza and the occupied West Bank in anticipation of mass protests.
Gaza's health ministry said more than 900 Palestinians were injured as demonstrators streamed to the border on the day the US prepared to open its embassy in Jerusalem.
Crowds built throughout the day in the besieged Palestinian enclave less than 100 kilometers away from Jerusalem and sealed off from Israel by a blockade.
At Shifa Hospital, where doctors say they are running low on crucial supplies and being forced to discharge patients early to make space for the next wave, a large tent was established outside in front of the emergency room.
At mosques in the cities, large speakers were set up that are expected to broadcast messages encouraging people to go to the border.
Earlier, Israeli army jets dropped leaflets over Gaza warning that those approaching the border fence "jeopardise" their lives.
One leaflet contained a photo of the Champs-Elysees boulevard in Paris and the caption: "Gaza 2025? The choice is in your hands."
Witnesses said Israeli drones dropped incendiary materials on the Gaza Strip setting ablaze tires that had been stockpiled to use in the protests.
Israeli Defence Minister Avigdor Lieberman said in a message to Gazans "we will protect our civilians with all our means and not enable the fence to be crossed."
Ninety-one Palestinians have been killed by Israeli fire since protests and clashes began along the Gaza border on March 30.
The protests are calling for Palestinian refugees who fled or were expelled during the 1948 war surrounding Israel's creation to be allowed to return to their homes now inside Israel.
No Israelis have been wounded and the military has faced criticism over the use of live fire.
East Jerusalem is considered occupied Palestinian territory under international law.
In the decades since Israel's 1967 occupation, international consensus has been that the city's status must be negotiated between the two sides, but Trump broke with that to global outrage.