“We are at war,” says Israel’s PM Benjamin Netanyahu, after a surprise Palestinian attack in the early hours of Saturday.
Dozens of gunmen from the militant group Hamas infiltrated Israel, sparking gun battles in several communities.
Videos on social media suggested Palestinian gunmen had carried out kidnappings.
At least 40 people in Israel were killed, with hundreds of others being treated in hospitals, according to emergency services.
More than 160 people have been killed in retaliatory Israeli strikes in the Gaza strip, officials there say.
Hamas commander Mohammed Deif says the Palestinian militant group had “decided to say enough is enough.”
