Backed by a barrage of rockets, dozens of Hamas militants broke out of the blockaded Gaza Strip and into nearby Israeli towns, killing dozens and abducting others in an unprecedented surprise early morning attack during a major Jewish holiday Saturday.

A stunned Israel launched airstrikes in Gaza, with its prime minister saying the country is now at war with Hamas and vowing to inflict an “unprecedented price.”

In an assault of startling breadth, Hamas gunmen rolled into as many as 22 locations outside the Gaza Strip, including towns and other communities as far as 15 miles from the Gaza border. In some places, they roamed for hours, gunning down civilians and soldiers as Israel’s military scrambled to muster a response. Gunbattles continued well after nightfall, and militants held hostages in standoffs in two towns.

Israel’s national rescue service said at least 200 people were killed and 1,100 wounded, making it the deadliest attack in Israel in decades. At least 198 people in the Gaza Strip have been killed and at least 1,610 wounded in Israeli strikes, the Palestinian Health Ministry said.

Hamas fighters took an unknown number of civilians and soldiers captive into Gaza, a deeply sensitive issue for Israel.

The conflict threatened to escalate to an even deadlier stage with Israel’s vows of greater retaliation. Previous conflicts between Israel and Gaza’s Hamas rulers brought widespread death and destruction in Gaza and days of rocket fire on Israeli towns. The situation is potentially more volatile now, with Israel’s far-right government stung by the security breach and with Palestinians in despair over a never-ending occupation in the West Bank and suffocating blockade of Gaza.

In a televised address Saturday night, Israeli Prime Minister Benjamin Netanyahu said the military will use all of its strength to destroy Hamas’ capabilities but the war will “take time.”

“We will defeat them … and take revenge for this black day,” he said.

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After nightfall, Israeli airstrikes in Gaza intensified, flattening several residential buildings in giant explosions, including a 14-story tower that held dozens of apartments as well as Hamas offices in central Gaza City. Israeli forces fired a warning just before, and there were no reports of casualties.

Soon after, a Hamas rocket barrage into central Israel hit four cities, including Tel Aviv and a nearby suburb, where two people were seriously injured. Throughout the day, Hamas fired more than 3,500 rockets, the Israeli military said.

The strength, sophistication and timing of the Saturday morning attack shocked Israelis. Hamas fighters used explosives to break through the border fence enclosing the Mediterranean territory, then crossed with motorcycles, pickup trucks, paragliders and speed boats on the coast.

In some towns, a trail of civilians’ bodies lay where they had encountered the advancing gunmen.

The shadowy leader of Hamas’ military wing, Mohammed Deif, said the assault was in response to the 16-year blockade of Gaza, Israeli raids inside West Bank cities over the past year, violence at Al Aqsa — the disputed Jerusalem holy site sacred to Jews as the Temple Mount — increasing attacks by settlers on Palestinians and growth of settlements.

“Enough is enough,” Deif, who does not appear in public, said in the recorded message. He said the attack was only the start of what he called “Operation Al-Aqsa Storm” and called on Palestinians from east Jerusalem to northern Israel to join the fight. “Today the people are regaining their revolution.”

The Hamas incursion on Simchat Torah, a normally joyous day when Jews complete the annual cycle of reading the Torah scroll, revived painful memories of the 1973 Mideast war practically 50 years to the day, in which Egypt and Syria launched a surprise attack on Yom Kippur, the holiest day of the Jewish calendar, aiming to take back Israeli-occupied territories.

Israel has maintained a blockade over Gaza since Hamas seized control of the territory in 2007. The bitter enemies have fought four wars since then.