Israeli troops fired tear gas and rubber bullets to repel them, but also live ammunition, the witnesses said
Israeli troops wounded nearly 50 Palestinians at the Gaza border on Wednesday during protests to mark the 71st anniversary of the "Nakba", or catastrophe, when many Palestinians lost their homes in the fighting around Israel's creation, Gaza officials said.
Thousands had gathered at the coastal enclave's frontier with Israel, the scene of bloodshed over the past year that has raised international concern.
Groups approached the border fence, planting Palestinian flags and throwing stones towards Israeli soldiers on the other side despite the efforts of marshalls in orange vests to keep protesters away from the barrier, witnesses said.
Israeli troops fired tear gas and rubber bullets to repel them, but also live ammunition, the witnesses said.
The Gaza Health Ministry said at least 47 people were wounded, though it was not clear how many of those were hit by live ammunition or were hurt by rubber bullets or by inhaling tear gas.
The Israeli military said about 10,000 rioters and demonstrators gathered in several places along the Gaza Strip fence.
"The rioters are setting tyres on fire and hurling rocks. A number of explosive devices have been hurled within the Gaza Strip, as well, and a number of attempts have been made to approach the security fence. IDF troops are responding with riot dispersal means."
Wednesday's rallies were called to mark Nakba Day, what Palestinians term the catastrophe that befell them at Israel's creation in 1948, when hundreds of thousands fled or were expelled from lands in what is now Israel.
"Our people rise today to announce their rejection to this crime and to assert their right in Palestine, all of Palestine," Islamic Jihad leader Khader Habib said at one demonstration, referring to Israel and the territories it captured in the 1967 Middle East war.
"Palestine is ours, the sea is ours, the sky is ours and the land is ours, and those strangers must be removed," he said.
Another protester, Jamila Mahmoud, 50, said her family had originally come from Asqlan, now the Israeli city of Ashkelon, near Gaza.
"If we don't return, maybe our children and grandchildren will do, one day we will get our rights back," Mahmoud said at the border protest site.
Palestinians also held rallies in the occupied West Bank but no major clashes with Israeli forces were immediately reported.
This year's Nakba protests were preceded by a surge in deadly cross-border fighting between Gaza militants and Israel which ended in a ceasefire on May 6.
Israeli troops have killed more than 200 Palestinians and wounded thousands in regular border protests since March 2018, according to human rights groups. UN investigators have said the Israeli military might be guilty of war crimes for using excessive force.
Israel has said it is defending its border against attacks against its troops and infiltration attempts by gunmen.
Israel has rejected a Palestinian right of return as a threat to maintaining a Jewish majority in a country it describes as the nation-state of the Jewish people.
Frustration is growing among Palestinians as hopes fade for a two-state solution to the conflict which would give them an independent country. President Donald Trump's announcement in December 2017 of US recognition of disputed Jerusalem as Israel's capital also fuelled Palestinian anger.