Gunmen from the Palestinian group Hamas have rampaged through Israeli towns, killing more than 200 people and escaping with hostages in by far the deadliest day of violence in Israel since the Yom Kippur war 50 years ago.
More than 230 Gazans were also killed when Israel responded with one of its most devastating days of retaliatory strikes.
“We will take mighty vengeance for this black day,” Prime Minister Benjamin Netanyahu said.
“Hamas launched a cruel and wicked war. We will win this war, but the price is too heavy to bear,” he said. “Hamas wants to murder us all. This is an enemy that murders mothers and children in their homes, in their beds. An enemy that abducts elderly, children, teenage girls.”
Hamas leader Ismail Haniyeh said the assault that had begun in Gaza would spread to the West Bank and Jerusalem.
“This was the morning of defeat and humiliation upon our enemy, its soldiers and its settlers,” he said in a speech.
“What happened reveals the greatness of our preparation. What happened today reveals the weakness of the enemy.”
Bodies of Israeli civilians were strewn across the streets of Sderot in southern Israel, near Gaza, surrounded by broken glass. The bodies of a woman and a man were sprawled across the front seats of a car.
Terrified Israelis, barricaded into safe rooms, recounted their plight by phone on live TV.
“They just came in again, please send help,” a woman identified as Dorin told Israel’s N12 News from Nir Oz, a kibbutz near Gaza. “My husband is holding the door closed … They are firing rounds of bullets.”
In Gaza, black smoke and orange flames billowed into the evening sky from a high-rise tower hit by an Israeli retaliatory strike.
Crowds of mourners carried the bodies of killed militants through the streets, wrapped in green Hamas flags.
Gaza’s dead and wounded were carried into crumbling and overcrowded hospitals with severe shortages of medical supplies and equipment. The health ministry said 232 people had been killed and at least 1700 wounded.
Streets were deserted apart from ambulances racing to the scenes of air strikes.
Israel cut the power, plunging the city into darkness.
Hamas said it fired a volley of 150 rockets towards Tel Aviv on Saturday evening in retaliation for an Israeli air strike that took down a high-rise building with more than 100 apartments.
Hamas deputy chief Saleh al-Arouri told al-Jazeera that the group was holding a large number of Israeli captives, including senior officials.
He said Hamas had enough captives to make Israel free all Palestinians in its jails.
The Israeli military confirmed Israelis were being held in Gaza.
A military spokesman said Israel could mobilise up to hundreds of thousands of reservists and was also prepared for war on its northern front against Lebanon’s Hezbollah group.
Hamas said the attack was driven by what it said were Israel’s escalated attacks on Palestinians in the West Bank, Jerusalem and against Palestinians in Israeli prisons.
“This is the day of the greatest battle to end the last occupation on earth,” Hamas military commander Mohammad Deif said, announcing the start of the operation in a broadcast on Hamas media and calling on Palestinians everywhere to fight.
In Gaza, a narrow strip where 2.3 million Palestinians have lived under an Israeli blockade for 16 years, residents rushed to buy supplies in anticipation of days of war ahead.
Some fled their homes and headed for shelters.
“We are afraid,” a Palestinian woman, Amal Abu Daqqa, told Reuters as she left her house in Khan Younis.
US President Joe Biden denounced the Palestinian attack and pledged support for Israel.
“This is not a moment for any party hostile to Israel to exploit these attacks to seek advantage. The world is watching,” he said.
A senior Biden administration told reporters that the United States was in intense talks with Israel about its particular needs as it responds to the attack.