Palestinians in Gaza have marched in their thousands to the Israel border at the start of a six-week-long protest.
The Palestinian health ministry says at least five people have been killed and 350 wounded, many of them by Israeli gunfire.
The Israeli military reported “rioting” at six places and said it was “firing towards main instigators”.
Palestinians have pitched five camps near the border for the protest, dubbed the Great March of Return.
What is the latest at the border?
The Israel Defense Forces (IDF) said there were about 17,000 Palestinians in five locations along the border fence.
The IDF said troops were “firing towards the main instigators” to break up rioting that included the burning of tyres and the throwing of Molotov cocktails and stones at the fence.
The IDF said it had “enforced a closed military zone” in the area surrounding Gaza.
Palestinian health officials said that among the dead was a 16-year-old boy.
They said that one of the five who died was killed before Friday’s protest started. Omar Samour, a 27-year-old farmer, was killed by Israeli tank fire near Khan Yunis.
Another man was wounded in that incident.
Witnesses say the two men were collecting parsley in a field, BBC Gaza producer Rushdi Abualouf reports.
Hamas, the militant group that dominates the Gaza Strip, has accused Israel of trying to intimidate Palestinians by killing the farmer and by urging them not to participate in the protests.
Addressing protesters, Hamas senior political leader Ismail Haniyeh said “we will not concede a single inch of the land of Palestine”.
He said: “There is no alternative to Palestine and no solution except to return.”
The Jerusalem Post also reported a rare public appearance by the leader of Hamas in Gaza, Yehiya Sinwar.
The Israeli military oversees a no-go zone along the Gaza border, citing security concerns, and has doubled its troop presence for the protest.It fears the protest could be an attempt at a mass breach of the border.
On the tank fire incident in Khan Yunis, an Israeli military spokesman said that “two suspects approached the security fence and began operating suspiciously and the tank fired towards them”.
The Israeli foreign ministry has said the protest is a “deliberate attempt to provoke a confrontation with Israel” and that “responsibility for any clashes lies solely with Hamas and other participating Palestinian organisations”.
Defence Minister Avigdor Lieberman took the unusual step of tweeting in Arabic, accusing Hamas of playing with citizens’ lives and warning people not to take part.
Palestinians have erected five main camp areas along the Israel border for the protest, from Beit Hanoun in the north to Rafah near the Egyptian border.
The Great March of Return protests were starting on Friday, as 30 March marks Land Day, which commemorates the killing of six protesters by Israeli security forces during demonstrations over land confiscation in 1976.
The protest is scheduled to end on 15 May, which Palestinians call Nakba (catastrophe) and which marks the displacement of hundreds of thousands of Palestinians during the conflict surrounding the creation of Israel in 1948.
Palestinians have long demanded their right to return but Israel says they should settle in a future Palestinian state in Gaza and the West Bank.