The Security Council on Friday convened an emergency session at Kuwait's request due to the situation in Gaza after 15 Palestinians were martyred by the Israeli army during a peaceful protest earlier in the day.
"There is fear the situation might deteriorate in the coming days," UN Assistant Secretary-General for Political Affairs Taye-Brook Zerihoun said at the emergency session and told the Council the UN would continue to stress that civilians should not be targeted and that all those involved refrain from placing children at risk.
He also demanded Israel fulfill its responsibilities under international law and emphasized that lethal force should be used only as a last resort, with any resulting fatalities properly investigated by the authorities.
Kuwait's permanent representative to the UN Mansour Al-Otaibi reasserted that Palestinian demonstrators were "unarmed" and stressed that the demonstrations were peaceful.
Al-Otaibi also condemned the deadly Israeli attacks.
U.S. diplomat Walter Miller encouraged both sides to take steps to prevent additional clashes and escalating tensions. "We are deeply saddened by the loss of lives in Gaza," he said.
Russia's permanent representative, Vladimir Safronkov, said Moscow was "deeply" concerned by the developments in Gaza.
"There is a real need to step up diplomatic mediation efforts in order to deescalate the situation," Safronkov added.
Separately, Secretary-General Antonio Guterres in a written statement called for an independent and transparent investigation into the clashes while the Security Council was conducting the emergency session.
Guterres expressed deep concern about the deadly clashes and urged restraint from any action that could lead to additional casualties, particularly measures that could place civilians in harm's way.
"This tragedy underlines the urgency of revitalizing the peace process aiming at creating the conditions for a return to meaningful negotiations for a peaceful solution that will allow Palestinians and Israelis to live side by side peacefully and in security," he added.
Tens of thousands of Gazans converged on the Strip's 45-kilometer (28-mile) long eastern border with Israel to reaffirm their right to return to their ancestral homes in historical Palestine.
Hours before the march, a Palestinian farmer was killed when an Israeli artillery shell struck his land in the southern Gaza Strip.
Israel deployed thousands of troops along the border in anticipation of the mass demonstrations dubbed "Great March of Return" that also sought to pressure Israel to lift its more than decade-long blockade of Gaza.
The rallies were endorsed by virtually all Palestinian political factions, which repeatedly stressed the event's peaceful nature.
Since 2007, the Gaza Strip has suffered from a crippling Israeli-Egyptian blockade that has gutted its economy and deprived more than 2 million residents of many vital commodities.
The rally Friday coincided with Palestinian Land Day that commemorates the murder of six Palestinians by Israeli forces in 1976.
