The U.N. chief is urging an immediate cease-fire between Israel and Gaza's Hamas rulers at the start of a U.N. General Assembly emergency meeting.
The session is expected to hear from about 100 speakers, including 12 ministers mainly from Arab and Islamic countries.
Secretary-General Antonio Guterres told Thursday's in-person meeting in the assembly chamber that he and the U.N. Mideast envoy are engaged in "extensive diplomatic efforts" in the region, including with Egypt, Jordan and Qatar, to stop the fighting.
He called on all members of the international community "to do everything in their power to enable the parties to conflict to step back from the brink."
The U.N. chief also called on Israel and Hamas "to allow for mediation efforts to intensify in order to bring the fighting to an end."
Guterres implicitly criticized Israel and Hamas for violating "the laws of war" which ban indiscriminate attacks and attacks against civilians and civilian property as well as attacks on military targets that cause disproportionate civilian casualties. He said "counter-terrorism or self-defense" are not justifications.
He urged Israeli authorities to abide by the laws, "including the proportionate use of force" and called on them "to exercise maximum restraint in the conduct of military operations." He urged Hamas and other groups "to stop the indiscriminate launching of rockets and mortars from highly populated civilian neighborhoods into civilian population centers in Israel."
