Israeli soldiers fired tear gas, rubber bullets and water cannons at Palestinians at Land Day rallies on Friday, killing a young man and wounding scores.
The young Gazan was killed in clashes between stone-throwing protesters and security forces at the Erez checkpoint which left at least five more people seriously injured, including a journalist.
Progressive Palestinian MP Mustafa Barghouti was rushed to a Ramallah hospital after being hit in the head by a tear gas canister at Qalandia checkpoint in the occupied West Bank, where youths threw stones and petrol bombs at Israeli security forces.
Police used ear-splitting sirens and water cannon firing foul-smelling liquid to break up their demonstration.
Palestinians who live in Arab east Jerusalem waved their national flag outside Jerusalem's walled Old City, chanting: "One, one homeland."
Supporters in neighbouring Arab countries also staged marches near the Israeli border, but organisers kept protesters away from the frontier.
In southern Lebanon more than 3,000 Lebanese and Palestinian people gathered outside the Crusader-built Beaufort castle nine miles from Israel. Lebanese security forces kept them from moving any closer to the border.
Sobhiyeh Mizari, 70, said she always taught her 12 children "never to forget Palestine.
"We will liberate our land against the will of Israel and its backers," said Ms Mizari, whose husband was killed in Israeli shelling of Lebanon in 1978.
Last year, Israeli troops opened fire on demonstrators from Lebanon and Syria who tried twice to break across the borders into Israel, killing at least 38 people.
The annual Land Day rallies commemorate six Israeli Arabs who were gunned down by Israeli soldiers on March 30, 1976 as they demonstrated against the Israeli expropriation of Arab-owned land in Galilee to build Jewish-only settlements.
Palestine Liberation Organisation official Saeb Erekat said on Friday the ongoing expansion of such settlements in the West Bank and east Jerusalem remains "at the heart of the conflict.
"For 44 years this policy of colonialism has been the main source of violence in the region and the single most menacing threat to the two-state solution," Mr Erekat said.
"The freedom defenders are marching for dignity toward Jerusalem. Together with them, Palestinians will continue their certain path toward national independence."
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