Pope Leo XIV slammed the "barbarity" of the war in Gaza on Sunday and urged against the "indiscriminate use of force", just days after a deadly strike by Israel's military on a Catholic church.

"I once again ask for an immediate end to the barbarity of the war and for a peaceful resolution to the conflict," Leo said at the end of the Angelus prayer at Castel Gandolfo, the papal summer residence near Rome.

The pope, who spoke by telephone with Israeli Prime Minister Benjamin Netanyahu the morning after Thursday's strike, spoke of his "deep sorrow" for the attack on the Holy Family Church.

The church was sheltering around 600 displaced people, the majority of them children and including dozens of people with special needs.

Israel expressed "deep sorrow" over the damage and civilian casualties, adding that the military was investigating the strike.

"This act, unfortunately, adds to the ongoing military attacks against the civilian population and places of worship in Gaza," Leo said on Sunday.

"I appeal to the international community to observe humanitarian law and respect the obligation to protect civilians, as well as the prohibition of collective punishment, the indiscriminate use of force, and the forced displacement of populations," he added.

The Israeli military on Sunday issued an evacuation order for Palestinians in the central Gaza Strip, warning of imminent action against Hamas militants.

Most of Gaza's population of more than two million people have been displaced at least once during the war, which is now in its 22nd month.

The pope also expressed his "sympathy" for the plight of "beloved Middle Eastern Christians" and their "sense of being able to do little in the face of this dramatic situation".