The Israel Defense Forces (IDF) said in a statement that orders calling up 60,000 reservists were issued on Wednesday as part of the preparations for “the next phase of Operation Gideon’s Chariots” – the offensive that it launched in May.

In addition, 20,000 reservists who had already been called up would receive a notice extending their current orders, it added.

The Israeli military official said senior commanders had approved the plan for a “gradual” and “precise” operation in and around Gaza City, and that the chief of staff, Lt Gen Eyal Zamir, was expected to finalise them in the coming days.

Five divisions are expected to take part in the offensive, according to the official.

The newspaper Haaretz quoted Defence Minister Katz as saying on Tuesday: “Once the operation is completed, Gaza will change its face and will no longer look as it did in the past.”

He also reportedly approved a plan to “accommodate” Gaza City residents in the south of the territory, including the coastal al-Mawasi area, where the military has begun establishing additional food distribution points and field hospitals.

Prime Minister Benjamin Netanyahu has said the military’s objectives are to secure the release of all the hostages held by Hamas and “complete the defeat” of the Palestinian armed group.

The IDF also announced on Wednesday that the Givati Brigade had resumed operations in the northern town of Jabalia and on the outskirts of Gaza City, where it said they were “dismantling military infrastructures above and below ground, eliminating terrorists, and consolidating operational control”.

It said civilians were being told to move south for their safety “to mitigate the risk of harm”.

A spokesman for Gaza’s Hamas-run Civil Defence agency, Mahmoud Bassal, told news agency AFP on Tuesday that the situation was “very dangerous and unbearable” in the city’s Zeitoun and Sabra neighbourhoods, where he said “shelling continues intermittently”.

The agency said Israeli strikes and fire had killed 21 people across Gaza on Wednesday.

Palestinian news agency Wafa reported that three children and their parents were killed when a house in the Shati refugee camp, west of Gaza City, was bombed.