In a message to the city's residents posted on social media, army spokesman Avichay Adraee said: "Take this opportunity to move early to the (Al-Mawasi) humanitarian zone and join the thousands of people who have already gone there."

Adraee did not specify when the new offensive would start, and another spokesman has previously said it would not be announced in advance to preserve the element of surprise.

The UN estimates there are about a million people in and around Gaza City, warning of a coming "disaster" if the Israeli military goes ahead with its plans to seize the city.

Israel has come under mounting pressure at home and abroad to call off the offensive and end the war in Gaza.

Its foe Hamas agreed to a ceasefire proposal last month that involved a temporary truce and the staggered release of hostages held in Gaza.

Israel, however, has demanded the Palestinian militant group release all the hostages at once, lay down its arms and give up control of Gaza, among other conditions.

In a separate statement Saturday, the military said the humanitarian zone in the south had essential "infrastructure such as field hospitals, water pipelines, and desalination facilities, alongside the continued supply of food, tents, medicines, and medical equipment".

It added the humanitarian efforts in the zone "will continue on an ongoing basis in cooperation with the UN and international organisations, in parallel to the expansion of the ground operation".

Israel first declared Al-Mawasi a safe zone early in the war, which was triggered by Hamas's October 7, 2023 attack.

However, the army has carried out numerous bombings in the area since then, saying it was targeting Hamas fighters hiding among civilians.

Dozens of Palestinians interviewed by AFP in Gaza City in recent weeks have said there is "no safe place" in the territory, with many saying they would rather die than be displaced again.