The Israeli army on Monday sent messages to thousands of Palestinians living near Gaza City to flee shortly after a mortar shell killed at least four people in Israel.

"A short while ago, phonecalls were made and text messages were sent out to the civilian population of Shejaiya, Zeitun and eastern Jabaliya calling them to evacuate immediately towards central Gaza City," a statement from the army said, referring to three areas to the north, south and east of Gaza City.