UNITED NATIONS (AP) — The U.N.'s top Mideast envoy warned Thursday that the Gaza Strip is "about to explode" and declared the world "must do everything possible to prevent another war" between Israel and the Palestinians as well as elsewhere in the Mideast.

Nickolay Mladenov told the U.N. Security Council that prospects for an Israeli-Palestinian peace are slipping further away and with tensions mounting, the "Israeli-Palestinian conflict remains a perpetual source of oxygen for militants and radicals" in the region.

His warnings came ahead of Friday's fifth weekly planned protests by Hamas, which controls Gaza, near the border fence with Israel, which has become a deadly flashpoint. Hamas says the protests are against a decade-long blockade of the isolated strip. Israel says it is defending its sovereign border and only targeting instigators and accuses Hamas of using the protests as a cover for attacks.

So far, 35 Palestinians have been killed by Israeli fire and more than 1,500 have been wounded since the protests began March 30 — a death toll that drew sharp criticism of Israel from many countries at Thursday's council meeting. Israel and its close ally, the United States, countered by accusing Hamas of using innocent civilians as human shields.

Mladenov called Gaza a "powder keg" and told council members that "old wounds continue to bleed and deepen as we speak, risking the outbreak of another war." He also stressed there is no military solution to any Mideast conflict — whether in Syria, Yemen or Gaza.

De-escalation is critical "in this highly charged and dangerous environment," he said. "Everyone in the Middle East needs to step back from the brink."

Describing the current situation in Gaza, Mladenov used some of his strongest remarks yet.

"What is happening in Gaza is an injustice that no man, woman or child should have to endure," he said. "People should not be destined to spend their lives surrounded by borders they are forbidden to cross, or waters they are forbidden to navigate. They should not be destined to live under the control of Hamas, which invests in militant activities at the expense of the population."

In addition to the killings by Israeli forces, he said there have been "an increasing number of dangerous incidents at the fence" by Palestinians, including planting improvised explosive devices — at least one which exploded — and throwing Molotov cocktails, as well as attempting to get through the fence.

The U.N. envoy said he has engaged intensively with all sides to reduce "risks of friction" and welcomed efforts by Egypt and others.

"Israel must calibrate its use of force and minimize the use of live fire. Lethal force should be used only as a last resort," Mladenov said. "Hamas and the leaders of the demonstrations must keep protesters away from the Gaza fence and to prevent all violent actions and provocations."

Riyad Mansour, the Palestinian U.N. ambassador, accused Israel's military forces of targeting civilians in Gaza and called their deliberate killing and wounding "terrorism."

He insisted the Friday demonstrations at the Gaza-Israel border were peaceful protests by Palestinians demanding "their dignity and freedom" — especially in Gaza where its 2 million inhabitants have been subjected to an Israeli land, sea and air blockade for a decade.

Israel's U.N. Ambassador Danny Danon accused Hamas of orchestrating provocations and confrontations along the security fence and using women and children as human shields.

Hamas "terrorists are hiding while allowing — even hoping — for their people to die," he said, calling this "evil in its purest form."

Danon said there is nothing peaceful about Palestinians putting explosives on the fence, firing over it, setting off firebombs, burning tires and throwing Molotov cocktails. Israel has an obligation to protect its citizens, he said, "and we will do so while minimizing casualties to the other side."

U.S. Ambassador Nikki Haley said using civilian as human shields is reaching "epic proportions" in the Middle East, accusing Hamas in Gaza and militants in Iraq, Lebanon, Syria and Yemen of hiding behind innocent men, women and children.

"Iran is the patron and protector of many of these groups that fight from behind the bodies of innocent civilians," she said.

Haley called the use of human shields a "barbaric practice," and said "the use of civilians to intentionally shield otherwise lawful military targets from attack is a war crime."

"For humanity's sake the Security Council must rise up to address this threat," she said.

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