The Israeli army dropped fliers over Gaza City urging residents to evacuate their homes on Wednesday.
The leaflets urged residents to stay away from Hamas militants and to report possible rocket launches. The fliers also gave a contact phone number and email.
Israeli tank shells killed at least 15 Palestinians and wounded 90 at a U.N. school sheltering Gaza refugees early on July 30, a health official and a spokesman for a U.N. aid agency said.