Israel vows expanded response if Gaza clashes go on as UN calls for investigation into Friday's violence

Israel warned Saturday of a stepped-up response if violent protests in Gaza continued as the head of the United Nations called for an investigation into Friday’s deadly clashes in the volatile border zone.

Palestinian health officials said 15 Palestinians were killed and more than 750 wounded by Israeli fire as protesters clashed with Israeli soldiers near the border fence separating Gaza and Israel.

Brig. Gen. Ronen Manelis, the chief army spokesman, denied allegations of excessive use of force, saying those killed by Israeli troops were men between the ages of 18 and 30 who were involved in violence and belonged to militant factions.

He alleged Gaza health officials exaggerated the number of those wounded and that several dozen at most were injured by live fire while the rest were merely shaken up by tear gas and other riot dispersal means.

Manelis reiterated Saturday that Israel "will not allow a massive breach of the fence into Israeli territory."

He said that Hamas and other Gaza militant groups are using the protests as a cover for staging attacks. If violence continues, "we will not be able to continue limiting our activity to the fence area and will act against these terror organizations in other places too," he said.

At the U.N. Secretary-General Antonio Guterres called for an independent and transparent investigation into the violence following an emergency meeting of the U.N. Security Council Friday evening.

The council didn't decide on any action or joint message after the emergency meeting.

Palestinian Ambassador Riyad Mansour said he was disappointed the Security Council didn't coalesce to condemn what he called a "heinous massacre" of peaceful demonstrators or to support his call to provide protection for Palestinian civilians.

"We expect the Security Council to shoulder its responsibility" and "defuse this volatile situation, which clearly constitutes a threat to international peace and security," Mansour said.

Israeli Ambassador Danny Danon said "the international community must not be deceived" by what he termed "a well-organized and violent terror-gathering" under the banner of a peaceful march.

"The Palestinians sunk to a new deceitful low so that they could use the U.N. to spread lies about Israel" while its representatives weren't there because of the Passover holiday, Danon said in a statement.

The U.S., which often complains about what it sees as anti-Israel bias at the U.N., urged all involved in the conflict to lower tensions.

"Bad actors who use protests as a cover to incite violence endanger innocent lives," added Walter Miller, an adviser at Washington's U.N. mission.

On Saturday, a few hundred people gathered at five tent encampments set up several hundred meters from the border fence. The tents serve as the launch points for marches.

Protest organizers have said mass marches would continue until May 15, the 70th anniversary of Israel's creation. Palestinians mark that date as their "nakba," or catastrophe, when hundreds of thousands were uprooted during the 1948 war over Israel's creation. The vast majority of Gaza's 2 million people are descendants of Palestinians who fled or were driven from homes in what is now Israel.

Four of those killed members of the Hamas military wing, the group said Saturday. The group said two people not counted in the official death toll were missing and presumed dead.

The Associated Press contributed to this report.