"It is important that we are able to turn this tragedy into an opportunity, and for this to be possible, it is necessary that we move decisively and irreversibly after the war towards a two-state solution," Guterres told reporters.

This requires "strengthening the Palestinian Authority to take responsibility for Gaza", he said. But "the Palestinian Authority cannot go to Gaza with Israeli tanks," so "the international community must consider a transitional period."

"I don't think a UN-sponsored protection system in Gaza is the solution. I think we need a multi-actor approach, so that different countries and entities cooperate," he said, noting that the United States is among these actors as the guarantor of "the security of Israel and Arab states in the region."

"Everyone must work together to create the conditions for a transition, allowing a strong Palestinian Authority to assume responsibilities in Gaza."

He again denounced "violations of international humanitarian law and violations of the protection of civilians in Gaza."

The high commissioner for human rights said on Sunday that the level of violence in the Gaza Strip in recent days was "unimaginable", with attacks on schools housing displaced people and a hospital turned into a "death zone".

Volker Türk said in a statement that "the horrific events that have taken place over the past 48 hours in Gaza are unimaginable."

"The deaths of so many people in schools that have become shelters, and the flight of hundreds to their lives from Shifa Hospital, amid the continued displacement of hundreds of thousands to southern Gaza, are actions that contravene the basic protection that must be provided to civilians under international law," he warned.