At least 40 Israelis were killed and 750 were injured, Al-Jazeera reported citing medical sources on Saturday, as Hamas launched a massive attack on Israel, briefly capturing localities around Gaza and taking dozens of Israelis prisoner.
Barrages of rockets were fired at Israel from the besieged Gaza Strip at dawn on Saturday, with at least one Israeli killed.
The Israeli newspaper Maariv reported that 140 Israelis were taken to Soroka Hospital in Beersheba, 20 of them in critical condition.
Israel also said that three towns near the Gaza Strip were under Hamas control, and Palestinian sources said that 35 Israelis had been captured by Hamas.
Rockets streamed across the sky repeatedly after the first launches from multiple locations across the blockaded Palestinian territory from 06:30 am (0330 GMT), AFP journalists in Gaza City reported.
The flare-up follows months of Israeli attacks in the occupied Palestinian territories, and repeated stormings by Israeli extremists of the Al-Aqsa Mosque in Jerusalem, with fatalities in West Bank hitting a scale not seen in years.
At least 247 Palestinians have been killed so far this year.
Air raid sirens could be heard across southern and central Israel, with the Israeli army urging the people to stay near bomb shelters.
The armed wing of the Palestinian group Hamas said it was behind the assault, claiming its militants had launched more than 5,000 rockets.
"We decided to put an end to all the crimes of the occupation (Israel), their time for rampaging without being held accountable is over," the Ezzedine al-Qassam Brigades said.
"We announce Operation Al-Aqsa Flood and we fired, in the first strike of 20 minutes, more than 5,000 rockets."
Hundreds of residents fled their homes in eastern Gaza to move away from the border with Israel, an AFP correspondent said.
Men, women and children were seen carrying blankets and food items as they left their homes, mostly in the northeastern part of the Palestinian territory, the reporter said.
Israel's military said Hamas launched "massive shooting of rockets", while at the same time "terrorists infiltrated into Israeli territory in a number of different locations".
Hamas "will face the consequences and responsibility for these events", it said in a statement.
The Palestinian militant group said its fighters seized an Israeli tank, a claim the army did not immediately comment on when contacted by AFP.
Footage broadcast by Hamas fighters from inside Israel showed a tank on fire.
An AFP photographer in the coastal city of Tel Aviv saw a gaping hole in a building, with residents gathered outside.
The office of Israeli Prime Minister Benjamin Netanyahu said he would shortly convene security chiefs following the Hamas attacks.
Hamas called on "the resistance fighters in the West Bank" as well as "our Arab and Islamic nations" to join the battle, in a statement posted on Telegram.
Israel has imposed a crippling blockade on Gaza since 2007 after Hamas took power, restricting travel, access to medicine and basic needs, and exacerbating poverty levels in the enclave which is home to 2.3 million people.
Gazan militants and Israel have fought several devastating wars since. In 2021, Israel launched a deadly assault on the enclave, which killed over 250 Palestinians. Thousands more were also displaced.
The latest violence follows a period of heightened tensions in September, when Israel closed the border to Gazan workers for two weeks.
The shutdown of the crossing came as Palestinian protests rocked the heavily militarised border. Israel responded with with tear gas and live bullets.
Resuming workers' passage on September 28 had raised hopes of calming the situation in Gaza.
In May, an exchange of Israeli air strikes and Gaza rocket fire resulted in the deaths of 34 Palestinians and one Israeli.
There has been an alarming rise in army raids and Israeli settler violence against Palestinians and their property, ever since Netanyahu's far-right cabinet came into power in December last year.
Several far-right Israeli ministers live in settlements in the West Bank, which are deemed illegal under international law.