At least 119 Palestinians, including 31 children, have been killed and more than 830 wounded since hostilities flared on Monday.
Hundreds of Palestinian families have taken shelter in UN-run schools in northern Gaza to escape Israeli artillery fire.
Israeli artillery and tank shells fired into Gaza on Thursday evening forced many families to flee their homes. Palestinians marked the first day of the Eid al-Fitr religious holiday under relentless aerial bombardment.
At least seven Israelis and one Indian national have also been killed. The Israeli army said hundreds of rockets were fired from Gaza towards Israel.
Israel massed additional soldiers and tanks near Gaza and Israel’s defence minister approved the mobilisation of 9,000 more reservist troops. But the armed forces maintained a ground offensive was not the primary focus of the operation against Palestinian fighters.