"To all residents of Gaza City... the defence forces are determined to defeat Hamas and will act with greater force in the Gaza City area," Colonel Avichay Adraee said in the post.

"Evacuate immediately via the Al-Rashid axis," he added, after Israeli Prime Minister Benjamin Netanyahu warned residents of the Gaza Strip's largest urban centre to leave.

Israel has been intensifying its bombardment of the city in preparation for an operation to take control of it, despite repeated entreaties from Western nations and aid agencies to stop.

"In two days we brought down 50 terror towers, and this is only the opening stage of the intensified ground manoeuvre in Gaza City. I say to the residents: you have been warned, leave now!" Netanyahu said in a video statement Monday evening.

"All of this is just a prelude, just the opening, to the main intensified operation -- the ground manoeuvre of our forces, who are now organising and assembling to enter Gaza City," he added.

Palestinian militant group Hamas said Netanyahu's threat amounted to an "explicit act of forced displacement" of Gaza City residents.

"It is taking place under the weight of bombardment, massacres, starvation, and threats of death-constituting a blatant and unprecedented challenge to international laws and conventions," Hamas said in a statement.

Gaza civil defence agency said Israeli air strikes continued overnight across Gaza City.