Pope Francis on Sunday appealed for peace as he kicked off Christmas celebrations with a mass at Saint Peter's Basilica as the Israel-Hamas war raged in the Gaza Strip.

"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 pope said to some 6,500 faithful who attended the traditional service.

Francis's address never mentioned Israel or Gaza by name, but he made numerous references to violence and war.

Palestinians held by the Israeli army in the Gaza Strip had suffered torture, two freed detainees and a medic said Sunday, a charged denied by the military.

The two men were among hundreds detained by Israeli forces over alleged links with armed group Hamas during Israel's ongoing ground offensive in the besieged Hamas-run territory.

Israel vowed to defeat Hamas after a deadly attack by militants on October 7, launching a relentless military campaign in Gaza.

Protesters marched Sunday through Morocco's capital in support of Palestinians, calling for an end to the Israel-Hamas war which has killed thousands in the Gaza Strip.

The crowd in Rabat of about 10,000 people denounced what protest leaders called a "war of extermination" as well as the normalisation of relations between Morocco and Israel.

The protesters were called to the streets by a disparate group of organisations backing the Palestinian cause, including left-wingers and members the Islamist Justice and Charity movement.

A pall of gloom descended over Bethlehem on Christmas Eve as the Gaza war weighed heavily on the biblical city in the occupied West Bank and the usual crowds of pilgrims stayed away.

The traditional giant Christmas tree, marching bands and flamboyant nativity scene were all absent in the city celebrated as the birthplace of Jesus Christ.

While there were few festive lights, a huge Palestinian flag was unfolded in the centre of town and a banner declared that "The bells of Bethlehem ring for a ceasefire in Gaza".

Gaza's deadliest ever war cast a pall of gloom over Bethlehem on Christmas Eve Sunday, as the death toll spiralled 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 October 7. Contacted by AFP, the Israeli army said it was "checking" the report.

Israel said its armed forces were increasingly focused on Hamas targets in south Gaza Sunday, as the United States again pressed its ally to do more to protect Palestinian civilians.

Signalling a pivot after weeks of intensive fighting around Gaza City, the Israeli army said troops were now looking to the Hamas stronghold of Khan Yunis and elsewhere in the south.

Christmas cheer has deserted the streets of Syria's cities, where the main churches have limited celebrations to prayers in solidarity with Palestinians suffering war in Gaza.

"In Palestine, the birthplace of Jesus Christ, people are suffering," the Syriac Catholic Archbishop of Aleppo, Mor Dionysius Antoine Shahda, told AFP.

The northern Syrian city's central district of Azizia is usually home to a bustling festive market and a huge Christmas tree, while its streets are adorned with lights and trinkets.

A relentless Israeli military campaign, in response to deadly Hamas attacks on October 7, has upset the lives of most, if not all, residents of the Gaza Strip.

Israeli forces have launched a bombardment campaign and ground invasion of Gaza ever since Hamas militants launched their shock attack -- the deadliest in Israel's 75-year history.

It killed about 1,140 people, mostly civilians, according to an AFP tally based on official Israeli figures.

Nearly three years after President Joe Biden took office vowing "America is back," the country's international image is taking a beating as his administration backs Israel in its war with Hamas.

In one step back from the newfound isolation, the United States on Friday, after painstaking negotiations, let through a UN Security Council resolution on humanitarian aid for the beleaguered Gaza Strip, after vetoing two earlier calls to halt the fighting.

President Joe Biden on Saturday pressed Israeli Prime Minister Benjamin Netanyahu to protect civilian lives in Gaza, the White House said, as the country's forces mounted fresh military strikes in the territory.

The conversation came a day after the UN Security Council passed a resolution demanding "safe and unhindered delivery of humanitarian assistance at scale," though it stopped short of calling for a ceasefire between Israel and Hamas militants.