Israel launched air raids in the Gaza Strip at dawn on Saturday after Hamas declared the start of Operation Al-Aqsa Flood in what is claimed to be one of the biggest attacks against Israeli occupation, also involving a surprise attack with gunmen crossing the border with a heavy barrage of rockets.
Israel's military said it was ready for war, adding it had carried out strikes against Hamas in Gaza and had called up reservists. Hamas militants said that it fired over 5,000 rockets into Israel.
At least one person's death has been confirmed while several are said to be injured. Reports of gunbattles in southern Israeli towns, affected by infiltration were also reported by the local media.
Daniel Hagari, Israeli army spokesman, said that more than 2,200 rockets have been fired into Israel since 6:30 a.m.
Hagari added that Hamas members infiltrated from land, sea and air.
The incident set off air raid sirens across the country, with Israel ordering residents to remain indoors as reports of various injuries and at least four deaths emerged.
Pictures showed armed men on vehicles inside Israel; there is also footage of Palestinian fighters taking Israelis hostage.
The Palestinian Ministry of Health says at least one person has been killed in an Israeli attack that hit the Indonesian Hospital in the northern Gaza Strip, adding that a number of people had also been wounded.
The missile launches came after a period of heightened tensions along the volatile Israeli-Gaza border and intense clashes in the Israeli-occupied West Bank.
Since Hamas, an Islamic militant group that opposes Israel, took control of Gaza in 2007, Israel has maintained a blockade on the territory. The adversaries have fought four wars since then.