GENEVA - Israel must stop the excessive use of force by its security forces along the Gaza border and must hold to account those responsible for the many deaths and injuries sustained by Palestinians in the past month, the UN human rights chief said on Friday.UN High Commissioner for Human Rights Zeid Ra'ad al-Hussein said in a statement that in the past four weeks, 42 Palestinians had been killed and more than 5,500 wounded along the fence in Gaza, with no reports of Israeli casualties."The loss of life is deplorable, and the staggering number of injuries caused by live ammunition only confirms the sense that excessive force has been used against demonstrators – not once, not twice, but repeatedly," Zeid said.Israel's Foreign Ministry said it did had no immediate comment on Zeid's statement. The government has said previously that it is doing what is necessary to stop the border fence being breached.International law permits the use of lethal force in cases of "extreme necessity" but it was hard to see how stones or Molotov cocktails thrown from a great distance at heavily protected security forces could constitute such a threat, Zeid said.The death toll includes 35 people killed during demonstrations as part of the "Great March of Return" - evoking a longtime call for refugees to regain ancestral homes in what is now Israel -- and appear to have been unarmed and no imminent threat to Israeli security forces, the statement said.The deaths could constitute wilful killings in the context of an occupation, a grave breach of the Fourth Geneva Convention, Zeid said.Four children were shot dead by Israeli forces, three of them killed by a bullet to the head or neck, he said. Another 233 children were injured by live ammunition, some sustaining injuries causing lifelong disabilities including amputations."It is difficult to see how children, even those throwing stones, can present a threat of imminent death or serious injury to heavily protected security force personnel," Zeid said.United Nations's warnings about excessive use of force appeared to have gone unheeded, with no change in Israeli tactics, and Israel only seem to carry out serious investigations when there was independent video evidence, he said. Otherwise there was little or no effort to apply the rule of law.Zeid said he was extremely concerned that by the end of the day, and forthcoming Fridays, the traditional day of protest, more Palestinians would be killed, simply because they approached a fence while exercising their right to protest."These trends call into question to what extent the [Israel security forces]’s rules of engagement, which are not public, are in line with international law, or at least to what degree the ISF abides by its own rules."