At least 22 killed in Hamas attack, Israel says at 'war' after rare militant infiltration from Gaza

At least 22 Israelis have been killed in the surprise attack launched by Palestinian Islamist Hamas on Saturday, Israel's N12 News reported, citing the Israeli ambulance service.

Palestinian militants have begun a ‘war’ against Israel which they infiltrated by air, sea and land from the blockaded Gaza Strip on Saturday, Israeli officials said, a major escalation in the Israeli-Palestinian conflict.

Prime minister Benjamin Netanyahu said "we are at war" and vowed severe retaliation after ordering an extensive mobilisation of Israeli army reserves. "The enemy will pay an unprecedented price," he warned.

Violence between Israel and the Palestinians has been surging since early last year, with fatalities in the occupied West Bank hitting a scale not seen in years.

"We decided to put an end to all the crimes of the occupation (Israel). Their time for rampaging without being held accountable is over," said the Ezzedine al-Qassam Brigades, the armed wing of Hamas which controls the Gaza Strip.

"We announce Operation Al-Aqsa Flood and we fired, in the first strike of 20 minutes, more than 5,000 rockets." Israel's army said its forces were fighting Palestinian militants on the ground in several locations near the Strip. It dubbed its operation "Swords of Iron".

Army spokesman Richard Hecht said the militants conducted a combined raid "which happened through paragliders, through the sea and through the ground." At least two people were killed in Israel, officials said.

"They are shooting at our house. They are trying to break down the door of the safe room," said one woman sheltering with her two-year-old child while her husband and other residents fought the militants in the streets of Kibbutz Sufa, according to Israeli media.

"Send help, please," she cried, according to the reports. Hamas later released a video showing three men captured by its fighters.

Militant infiltration from Gaza, an impoverished enclave home to 2.3 million people, have been rare since Hamas took control in 2007, leading to Israel's crippling blockade. Gaza is sealed off from Israel by a militarised border barrier.

The rocket barrage from Gaza -- which Hecht said numbered at least 2,200 -- left cars burning beneath residential buildings in the Israeli city of Ashkelon, about 10 kilometres (six miles) north of Gaza.

The attack occurred on Shabbat and during a Jewish holiday. Netanyahu said in a statement Hamas had launched a "murderous surprise attack" against Israel and its people. The Israeli leader said he had "ordered an extensive mobilisation of reserves" and fire would be returned at "a magnitude that the enemy has not known".

Israeli Major General Ghasan Alyan warned Hamas had "opened the gates of hell" and would "pay for its deeds". AFP journalists said Israel's military began air strikes on Gaza, following the rocket barrage from inside the territory.

"Dozens of IDF fighter jets are currently striking a number of targets belonging to the Hamas terrorist organisation in the Gaza Strip," the military said. Rockets had streamed across the sky after the first launches from multiple locations across the Palestinian territory from 6:30 am (0330 GMT), AFP journalists in Gaza City reported.

An AFP journalist saw armed Palestinians gathered around an Israeli tank, which was partially in flames, after they crossed the border fence from Khan Yunis in Gaza. Another AFP journalist saw Palestinians returning to Gaza City driving a seized Israeli Humvee.

Air raid sirens wailed across southern and central Israel, as well as an unusual number of times in Jerusalem, where AFP journalists heard multiple rockets being intercepted by Israeli air defence systems. The army urged people to stay near bomb shelters.

Israeli police set up roadblocks to check motorists on the highway between Tel Aviv and Jerusalem, an AFP journalist said.

Hundreds of residents fled their homes in Gaza to move away from the border with Israel, mostly in the northeastern part of the territory, an AFP correspondent said, adding the men, women and children carried blankets and food.

In the Israeli commercial centre of Tel Aviv, residents were seen boarding a bus to seek safety in a hotel. An AFP photographer in the city saw a gaping hole in a building, with residents gathered outside.

In Israeli-annexed east Jerusalem, some Palestinian residents cheered and blew their car horns as sirens blared. A regional council for Israeli communities northeast of Gaza said its president was killed in an exchange of fire with attackers from Gaza.

Separately, a woman in her 60s was killed "due to a direct hit" in Israel, the Magen David Adom emergency services said. Fifteen others were wounded, two of them seriously, medics said.

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.

Lebanese militant group Hezbollah, which fought a devastating war against Israel in 2006, hailed the Palestinians' "heroic operation on a grand scale". Western capitals roundly denounced the Palestinian attacks on Israel.

The United States condemned the Hamas fire and urged "all sides to refrain from violence and retaliatory attacks." Palestinian militants and Israel have fought several devastating wars since.

The latest violence follows heightened tensions in September, when Israel closed the border to Gazan workers for two weeks.

The shutdown of the crossing came as Palestinian demonstrators along the border burned tyres and threw rocks and petrol bombs at Israeli troops, who responded 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 killed 34 Palestinians and one Israeli.

Before Saturday's violence at least 247 Palestinians, 32 Israelis and two foreigners have been killed in the conflict, including combatants and civilians on both sides, according to Israeli and Palestinian officials.

The vast majority of fatalities have occurred in the West Bank, which has been occupied by Israel since the 1967 Arab-Israeli War.

There has been a rise in army raids, Palestinian attacks targeting Israelis and Israeli settler violence against Palestinians and their property.

This year's surging violence came against the backdrop of divisive judicial reforms introduced by the hard-right government of President Benjamin Netanyahu, who is on trial for corruption charges he denies.

Several far-right ministers in Netanyahu's cabinet live in West Bank settlements deemed illegal under international law.