Israeli soldiers fired live bullets and tear gas as activists across the frontier fences burned tyres and threw stones. 

The clashes broke out days before weeks of protests, aimed at ending a decade-old blockade of Gaza, culminate in a planned mass march expected to involve tens of thousands of people.

At least 146 protesters were wounded by live fire, seven of them critically, including a 16-year-old boy who was shot in the head, Gaza health officials said. Dozens more were overcome by tear gas.

It comes after Save the Children said more than 250 children had been shot by the Israeli army during the six previous Friday demonstrations.

Forty-four Palestinian protestors have been killed and more than 2,000 wounded by Israeli army fire since the weekly protests led by Gaza's ruling group Hamas began in late March.

Israel has faced international condemnation over its response to the demonstrations, but says it has the right to defend its borders. It insisted its gunmen only targeted the "main instigators" of violence and protesters who approach the border fences.

There are fears of further casualties after the leader of Hamas in the Gaza strip hinted that thousands of Palestinians could breach the border fence at Monday's march.

Comparing the enclave’s people to a “starving tiger”, Yahya Sinwar said: “What’s the problem if hundreds of thousands storm this fence which is not a border of a state? What’s the problem with that?“ 

Israel has warned it will prevent any border breach during the protests, which are part of a campaign to break the blockade imposed by Israel and Egypt after the Islamic militant Hamas took control of Gaza in 2007.

The six weeks of demonstrations will come to and end with a large-scale protest planned for Tuesday, when Palestinians mark their "nakba," or catastrophe, referring to their mass uprooting during the Middle-Eastern war over Israel's 1948 creation. Hundreds of thousands of Palestinians were driven out or fled homes in what is now Israel, and more than two-thirds of current Gaza residents are descendants of refugees.

On Friday, thousands of protesters gathered in five tent camps set up weeks ago, each several hundred metres from the border. From there, smaller groups moved closer to the border fence. 

One man was shot dead while protesting east of Khan Younis in southern Gaza, said medics.

Israeli soldiers fired live rounds and volleys of tear gas. Witnesses said Israeli forces on the other side of the fence had added reinforcements, including cement slabs, as protective cover. In recent weeks, soldiers have fired from behind sand berms.

More than 500 children have been injured during the border protests, more than half of them wounded by live bullets, according to Save the Children's analysis of data from the Palestinian health ministry.

Four children have been killed, including 14-year-old Mohammad Ayyoub, whose shooting prompted condemnation and demands for an investigation from the United Nations (UN) and European Union. 

Children wounded by Israeli gunfire include a 16-year-old track athlete whose leg was amputated after being shot, Save the Children said.

"We are deeply concerned by the high number of children who have been hit by live ammunition and we agree with the High Commissioner for Human Rights that this could suggest an excessive use of force and may amount to unlawful killing and maiming,” said Jennifer Moorehead, the charity's director for occupied Palestine territory.

She added: "We support the UN secretary-general’s call for independent investigations to be carried out and any perpetrators to be held to account. We strongly urge all protests to remain peaceful, and call on all sides to tackle the long-term causes of this conflict and promote dignity and security for both Israelis and Palestinians.” 

UN secretary-general Antonio Guterres has called for an "independent and transparent investigation" into the killings, while the UN High Commissioner for Human Rights said a "staggering number" of injuries had been caused by live ammunition.

Israel accused Hamas of using children as human shields in the protests, which it claimed were a front for attacks. 

Save the Children said its workers had seen children who had been repeatedly shot in the legs, arms and chest by Israeli forces. Victims also faced rapidly deteriorating conditions in hospitals, the charity warned.

“Gaza has been under an Israeli air, sea and land blockade for more than 10 years and has suffered three wars from which it has never fully recovered,” said Ms Moorehead.

Palestinian officials have announced that Egypt will open its border with Gaza for four days from Saturday. Egypt has kept the Rafah crossing point, Gaza's main gate to the outside world, closed most of the time since the Hamas takeover to reinforce Israel's blockade.

Egypt opens the crossing from time to time, mainly to allow people in special categories, including medical patients and Gaza residents studying abroad, to leave the territory or return.

The upcoming opening was framed as a humanitarian gesture ahead of the Muslim fasting month of Ramadan, which begins next week. 

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