Palestinians are fleeing parts of Gaza City after the Israeli military began the first stages of a planned ground offensive, officials in the city said.

Israel's troops have established a foothold on the outskirts of the city - which is home to more than a million Palestinians - after days of intense bombing and artillery fire.

It has prompted UN Secretary General António Guterres to renew calls for an immediate ceasefire "to avoid the death and destruction" an assault would "inevitably cause”.

A military spokesman said troops were already operating in the Zeitoun and Jabalia areas to lay the groundwork for the offensive, which Defence Minister Israel Katz approved on Tuesday and which will be put to the security cabinet later this week.

In a statement, Hamas accused the Israeli leader of continuing a "brutal war against innocent civilians in Gaza City" and criticised what it said was his "disregard" for a new ceasefire proposal from regional mediators. Israel has yet to formally respond to the plan.