The Israeli army called up reserves and carrying out air strikes on the Gaza Strip, after Hamas launched an unprecedented surprise attack on Saturday morning.
Dozens of rockets was launched from Gaza Strip towards Israel early on Saturday, as air raid sirens sounded across the country, according to several eyewitnesses.
Hamas fighters infiltrated the city of Sderot in southern Israel and clashed with soldiers.
They also launched rockets from the Gaza Strip against Tel Aviv, Sde Boker, Arad, Dimona, and Jerusalem.
At least five have been reported killed and 100 wounded.
Hamas has named the surprise attack Operation Al-Aqsa Flood.