Gaza's deadliest-ever war cast a pall of gloom over Bethlehem on Christmas Eve Sunday, as the death toll spiraled and Israel shifted its efforts against Hamas to the besieged territory's south.

The health ministry in the Hamas-run Strip said an Israeli strike late Sunday killed at least 70 people in Al-Maghazi refugee camp, in central Gaza, and destroyed several houses.

AFP was unable to independently verify the toll, which suggests one of the deadliest strikes since the war began on 7 October. Contacted by AFP, the Israeli army said it was "checking" the report.

Health ministry spokesman Ashraf al-Qudra said the "toll is likely to rise" as many families were thought to be in the area at the time of the strike.

Christmas celebrations were effectively canceled in the occupied West Bank city of Bethlehem, revered as the birthplace of Jesus Christ, where the Latin patriarch offered a message of solidarity with the Palestinians of Gaza.

And Pope Francis kicked off mass at Saint Peter's Basilica with a call for peace.

"Tonight, our hearts are in Bethlehem, where the Prince of Peace is once more rejected by the futile logic of war, by the clash of arms that even today prevents him from finding room in the world," the Catholic leader said.

US President Joe Biden earlier stressed the "critical need" to protect civilians, in a call with Prime Minister Benjamin Netanyahu, who vowed Israel would "continue the war until all of its goals have been achieved", according to official statements.

As heavy fighting raged on, the Israeli army said 154 troops had died in Gaza since it launched its ground invasion on 27 October.

Ten soldiers were killed in battles on Saturday, one of the deadliest days for the Israeli side.

"The war is exacting a very heavy price… but we have no choice but to keep fighting," said Netanyahu.

Christmas 'canceled'