Israeli troops have shot and wounded 30 Palestinians during a large protest on the Gaza-Israel border in which demonstrators hurled stones and burning tyres near the frontier fence, Palestinian medics say.
Some in the Gaza crowd threw firebombs and an explosive device, according to the Israeli military.
Thousands of Palestinians arrived at tented camps near the frontier on Friday as a protest dubbed "The Great March of Return" - evoking a longtime call for refugees to regain ancestral homes in what is now Israel - moved into its third week.
Israeli troops have shot dead 30 Gaza Palestinians and wounded hundreds since the protests began, drawing international criticism of the lethal tactics used against them.
An Israeli military spokesman said troops were being confronted by rioters and "responding with riot dispersal means while also firing in accordance with the rules of engagement".
On Friday, groups of youths waved Palestinian flags and burnt hundreds of tyres and Israeli flags near the fenced-off border after Friday prayers.
Israel has declared a no-go zone close to the Gaza border fence, and deployed army sharpshooters along it.
No Israelis have been killed during the demonstrations, and human rights groups say the Israeli military has used live fire against demonstrators who pose no immediate threat to life.
Israel says it is doing what it must to defend its border, and to stop any of the protesters getting across the fence.
The planned six-week protest has revived a longstanding demand for the right of return of Palestinian refugees to towns and villages from which their families fled, or were driven out, when the state of Israel was created 70 years ago.
The protest began on March 30, and is expected to culminate on May 15.
That is the day Palestinians will mark the 70th anniversary of the "Nakba" or "Catastrophe", when hundreds of thousands of Palestinians were displaced amid violence culminating in war between newly created Israel and its Arab neighbours in May 1948.
Successive Israeli governments have ruled out any right of return, fearing the country would lose its Jewish majority.
"Some people believe we are idiots to think the Israelis will allow us in, they may not, but we will not stop trying to return," said a protester, 37-year-old civil servant Ahmed, as he stood on a hilltop overlooking the Israeli fence.
Like most of the 2 million Palestinians packed into the tiny, impoverished Gaza Strip, Ahmed is a descendant of refugees from Jaffa, a coastal town in Israel just south of Tel Aviv.
The Israeli government accuses Hamas, the Islamist movement that has ruled Gaza largely since Israeli soldiers and settlers withdrew in 2005, of having instigated the protests and of using them as cover to launch attacks.
"Israel will continue to defend its borders and its citizens. Your country would do the same," an Israeli foreign ministry spokesman said on Twitter.
