Over 1,400 protesters were wounded, the Palestinian Health Ministry said, most of them hit by live bullets, tear gas shells, and rubber-coated steel pellets.
At least 16 Palestinians were killed and hundreds injured on Friday by Israeli security forces confronting one of the largest Palestinian demonstrations along the Israel-Gaza border in recent years, Gaza medical officials said.
Tens of thousands of Palestinians, pressing for a right of return for refugees to what is now Israel, gathered along the fenced 65-km frontier where tents were erected for a planned six-week protest, local officials said. The Israeli military estimate was 30,000.
The United Nations (UN) Security Council was briefed on the violence in Gaza on Friday at the request of Kuwait. Palestinian UN envoy Riyad Mansour told the council at least 17 Palestinian civilians were killed and more than 1,400 injured.
The council did not decide on any action or joint message after an emergency meeting Friday evening. Kuwait convened it hours after the bloodiest day in Gaza since the 2014 cross-border war between Israel and Hamas, the Islamic militant group that rules the coastal strip.
UN Secretary-General Antonio Guterres called for an independent investigation into the deadly clashes.
TRT World's Arabella Munro reports.
Annual "Land Day" protest
The Palestinian protest marked "Land Day," an annual commemoration of the deaths of six Arab citizens of Israel killed by Israeli security forces during demonstrations over government land confiscations in northern Israel in 1976.
The demonstrators demanded that Palestinian refugees be allowed the right of return to towns and villages which their families fled from, or were driven out of, when the state of Israel was created in 1948.
They gathered at multiple sites throughout the blockaded territory, which is flanked by Israel along its eastern and northern borders.
Smaller numbers approached within a few hundreds metres of the heavily fortified border fence, with Israeli troops using tear gas and live fire to force them back.
TRT World spoke to Wael al Zayat, a Middle East policy expert, on what the latest developments entail for peace in the region.
Turkey condemns Israel
Turkish foreign ministry expressed outrage over the killings in Gaza, in a statement on Friday.
"We condemn Israel for using disproportionate forces on peaceful Palestinian demonstrators. We are concerned for the people who lost their lives and injured in Israeli security forces intervention," the statement said.
"Israel must stop activities that increase tension in the region as soon as possible. We invite international communities to put their utmost effort to dissuade Israel from such aggression."
Hamas hails turnout
Hamas spokesman Fawzi Barhoum praised the turnout.
"The large crowds ... reflect the Palestinian people's determination to achieve the right of return and break the siege and no force can stop this right," he said.
Earlier in the day, before the main protests began, a Palestinian farmer was killed by Israeli tank fire near the border, the health ministry said.
The Israeli military said the tank fire came after "two suspects approached the security fence ... and began operating suspiciously."
Witnesses said the military had used a drone in at least one location to drop tear gas.
The Israeli military said thousands participated in the clashes, and that troops opened fire at the "main instigators."
"The rioters are rolling burning tyres and hurling firebombs and rocks at the security fence and at (Israeli) troops, who are responding with riot dispersal means and firing towards main instigators."
Israeli tanks and snipers were positioned on the other side of the border, using tear gas and live fire to force back the protesters.
Earlier, TRT World spoke with journalist Muhannad Alami in the occupied West Bank and Muhammad Mansour in Gaza.
'No solution except to return'
Among those taking part on Friday was Ismail Haniya, the leader of the Hamas that rules Gaza.
"There is no alternative to Palestine and no solution except to return," he said in a statement, referring to Palestinian refugees seeking to go back to land they fled or were expelled from in 1948 that is now inside Israel.
Israel has accused Hamas of seeking to stir up protests to encourage violence.
Israeli forces open fire on thousands of Palestinians, who had gathered near the Gaza-Israel border to protest against the planned US embassy move to Jerusalem, killing seven protestors and wounding more than 500 others pic.twitter.com/yg8Wjt7Nvj— TRT World (@trtworld) March 30, 2018
Protest in occupied West Bank
There were also small protests in the Israeli-occupied West Bank.
But the main focus was Gaza, from which Israeli soldiers and settlers withdrew in 2005 after 38 years.
The Gaza Strip is now ruled by the Hamas and blockaded by Israel.