An Israeli strike flattened a high-rise in Gaza City on Saturday -- the second in as many days -- after the military warned people to flee south to a "humanitarian zone" ahead of a planned offensive against the urban hub.

Israel has been warning for weeks of a new assault on the territory's largest city, without issuing a timeline.

It has stepped up air strikes and ground operations on the city's outskirts, sparking fears it could worsen already dire conditions.

On Saturday, Israeli aircraft dropped thousands of leaflets on western neighbourhoods calling on residents to evacuate, witnesses and an AFP journalist said.

Nafez Anis, who has been living in a tent with his family in Gaza City, said he had read the leaflet, but was not planning on leaving.

"Where should we go?" he told AFP.

See Full Page