Pope Francis called for an end to the Hamas-Israeli conflict amid fears it could widen, and called for more humanitarian aid to be allowed into to the Gaza Strip.

War is always a defeat, it is a destruction of human fraternity. Brothers, stop! Stop!" Francis said after his traditional Angelus prayer in Rome's Saint Peter's Square.

"I renew my call for spaces to be opened, for humanitarian aid to continue to arrive and for hostages to be freed," the 86-year-old pontiff said.

Israel's retaliatory bombing campaign has killed more than 4,300 Palestinians, mainly civilians, according to the Hamas-run health ministry, and reduced swathes of densely populated Gaza to smouldering ruins.

Alarm has grown about a humanitarian crisis in Gaza, where Israel has cut off water, food and power.