After a significant surprise strike with militants entering Israel from Gaza while under heavy rocket fire, at least 22 people have died in Israel.
Unverified allegations claim that some Israelis have been abducted and transported back into Gaza.
In response, Israel has carried out a series of airstrikes on targets in Gaza.
Israel is “at war,” according to Israeli Prime Minister Benjamin Netanyahu, who also promised that Gaza’s rulers, Hamas, will “pay a price it has never known.”
Just as the sun was rising, the militants scaled the perimeter fence as a barrage of missiles was unleashed from Gaza.
The Israeli military has reportedly called up tens of thousands of reservists and claimed that dozens of fighter jets are conducting airstrikes on Hamas targets in Gaza.
Local health officials report that at least one Palestinian has died as a result of the strikes.
Saturday, the Jewish Sabbath and the day of the festival of Simchat Torah, saw the start of the rocket attacks from Gaza just after sunrise.
The IDF reported that “terrorists” had entered Israeli land “in a number of different locations” as sirens wailed throughout Israel.
It advised residents of the southern and central regions to remain close to shelters and within shelters in the vicinity of Gaza.
Online videos appeared to show a pick-up vehicle being driven around Sderot by a gang of highly armed Palestinian terrorists wearing black fatigues.
The same militants appeared to be exchanging fire with Israeli troops in one video in the town’s streets, which is only 1.6 kilometers (miles) from Gaza.
A number of Israelis have reportedly been kidnapped by terrorists, according to unsubstantiated allegations in the Palestinian media, and there is video circulating of Palestinians in Gaza operating Israeli military equipment.
Palestinians gathered close to an Israeli tank that was set ablaze on the border barrier between Israel and Gaza.
Israel’s health ministry reports that the Hamas attacks have left 545 Israelis injured.
But the leader of one regional council in southern Israel, Ofir Liebstein, was killed in an exchange of fire with militants when he went to defend his community.
The rocket barrages meanwhile continued throughout Saturday morning, with Israeli media reporting that more than 2,500 projectiles had so far been launched towards Israel.
Hospitals in the southern city of Ashkelon and central city of Beer Sheva are treating casualties.
“Citizens of Israel we are at war, not an operation, not an escalation, a war,” Prime Minister Netanyahu said in a statement. “This morning Hamas launched a murderous surprise attack against the state of Israel and its citizens.”
“I convened the heads of the security system, first of all I instructed to cleanse the settlements of the terrorists who had infiltrated – this operation is being carried out during these hours.”
“At the same time, I ordered an extensive reserve mobilisation and a retaliatory war with a strength and scope that the enemy has never known.”
A senior Hamas military commander announced the start of the operation in a broadcast on Hamas media, calling on Palestinians everywhere to fight.
“This is the day of the greatest battle to end the last occupation on Earth,” Mohammed Deif said.