Pope Francis on Sunday appealed for peace in Gaza during his weekly Angelus prayer, calling for "concrete gestures to build peace" as the deadly six-day offensive escalated.
In an address to thousands of pilgrims on St Peter's Square Francis spoke of the "tragic events of the last few days".
Francis visited the Middle East in May and held a joint prayer in the Vatican with Israeli President Shimon Peres and Palestinian president Mahmud Abbas in June.
"I urge all interested parties and all in local and international political office not to spare in prayer and efforts to cease all hostilities," Francis said.
Referring to the June 8 joint prayer, he said: "Some people might think that such a meeting was in vain. But this is not the case because prayer helps us not to be conquered by evil or resign ourselves to violence and hatred."
As world powers prepared to meet in Vienna over the escalating conflict, the Palestinian death toll from Israel's punishing air campaign hit 165 following the bloodiest day yet, which left 56 people dead.
So far, no Israelis have been killed, although militants in Gaza have pounded the south and centre of the country with more than 630 rockets since the fighting began on July 8, in the biggest Israel-Hamas confrontation since 2012.