Pope Francis on Monday condemned "war crimes" perpetrated against civilians in conflicts such as in Gaza and Ukraine, and said those killed should not be considered "collateral damage".

"The distinction between military and civil objectives is no longer respected," the 87-year-old pontiff said in his New Year's address to diplomats at the Vatican.

"There is no conflict that does not end up in some way indiscriminately striking the civilian population. The events in Ukraine and Gaza are clear proof of this," he added.

"We must not forget that grave violations of international humanitarian law are war crimes", he continued, in a speech dominated by calls for an end to conflicts around the world.

Francis said people "need to realise more clearly that civilian victims are not 'collateral damage' but men and woman, with names and surnames, who lose their lives."

"Were we to be able to look each of them in the eye, call them by name, and learn something of their personal history, we would see war for what it is -- nothing other than an immense tragedy," he said.

- 'Inconceivable suffering' -

"I renew my condemnation of this act and of every instance of terrorism and extremism," the pope said, in reference to Hamas' attack on October 7.

Israeli Occupation has responded since October 7 with relentless bombardment of Gaza and a ground invasion that have killed at least 22,835 people, most of them women and children, according to the Gaza health ministry.

The pontiff said Israeli Occupation's "strong" military response "has caused an exceptionally grave humanitarian crisis and inconceivable suffering."

"To all the parties involved, I renew my appeal for a ceasefire on every front... and the immediate liberation of all the hostages held in Gaza," Francis said.

"I ask that the Palestinian people receive humanitarian aid, and that hospitals, schools and places of worship receive all necessary protection," he added.

Most of Gaza's population has been displaced, according to the United Nations, leaving them in overcrowded shelters or tents in the winter cold.

The World Health Organization has warned of the risk of famine and disease, with people struggling to find food, safe water, fuel and medicine.

On Sunday, the UN reported "sickening scenes" at Al-Aqsa hospital, one of the only ones in Gaza that is still partly functioning, with "people of all ages being treated on blood-streaked floors and in chaotic corridors."