Dozens of Israelis — including soldiers and civilians — are believed to have been taken hostage by Hamas militants.
BBC reports that at least 70 people in Israel have been confirmed killed, with hundreds of others undergoing treatment in hospitals.
Other media reports put the Israeli death toll at 100.
Nearly 200 people have been killed in retaliatory Israeli strikes in the Gaza strip.
Early Saturday, members of the Hamas militant group launched an unprecedented attack on Israeli territory.
Mohammed Deif, Hamas military commander, said Hamas had fired more than 5,000 rockets into Israel in what he called “Operation Al-Aqsa Storm”.
He said the attacks were in retaliation for Israel’s “desecration” of the Al-Aqsa Mosque in Jerusalem, adding that Israel has killed and wounded hundreds of Palestinians this year.
Israel’s Prime Minister Benjamin Netanyahu has declared that his nation is at war.
“The enemy will pay a price he has never known. In the meantime, I call on all citizens of Israel to strictly obey the instructions of the army and the instructions of the Home Command,” Netanyahu said.
