Continued crossfire between Israeli forces and militant groups including Hamas is "unacceptable," Secretary-General Antonio Guterres told the UN General Assembly Thursday, saying "the fighting must stop immediately."

"I am deeply shocked by the continued air and artillery bombardment by the Israeli Defence Forces in Gaza," Guterres said of the salvos that he said have killed "at least 208 Palestinians, including 60 children."

The Gaza health ministry has put the toll slightly higher, at 230 Palestinians killed, 65 of them children. 

Guterres continued that "indiscriminate firing of rockets by Hamas and other militant groups towards population centres in Israel, resulting in at least 12 fatalities including two children, and hundreds of injuries, is also unacceptable." 

The toll given by Guterres differs from that given by Israeli police, which says Hamas rockets have claimed 12 lives including one child.

"If there is a hell on earth, it is the lives of children in Gaza," Guterres said.

The General Assembly meeting was requested by Niger and Algeria, respectively the current chairs of the Organization of Islamic Cooperation and the Arab Group at the United Nations.

"It is imperative that we achieve de-escalation, to prevent an uncontainable crossborder security and humanitarian crisis," he said, calling for the "resumption of negotiations" pursuing "a two-state solution on the basis of the 1967 lines."

On Wednesday, the 10th day of deadly violence between Israel and armed Palestinian groups in Gaza, a spokesperson for the Secretary-General said Guterres had had contact with Palestinians and officials in the Middle East, but not yet with Israeli Prime Minister Benjamin Netanyahu.

Denouncing airstrike damage to "several hospitals," the UN chief also called the levelling of media offices as well as the killing of a journalist in Gaza "extremely concerning."

"I am deeply distressed by damage to United Nations facilities in Gaza," he said. "United Nations premises are inviolable, including during armed conflict. Humanitarian installations must be respected and protected."

He said an appeal for humanitarian aid donations would launch "as soon as possible," specifying that the UN would release $14 million from the Humanitarian Fund for the Occupied Palestinian Territories.

"There is no justification, including counterterrorism or self-defense, for the abdication by the parties to the conflict of their obligations under international humanitarian law," Guterres said.

"I am also deeply concerned by the continuation of violent clashes between Israeli security forces and Palestinians across the occupied West Bank, including East Jerusalem, where several Palestinian families are under the threat of eviction."

A years-long bid by Israeli settlers to take over Palestinian homes is among the origins of the escalation in violence between Israel and Hamas that began May 10.