Israeli soldiers fought to repel Hamas militants Sunday and exchanged fire with the Lebanese militant group Hezbollah, raising the prospect of a broader regional conflagration a day after an unprecedented surprise attack on southern Israel by Palestinian militants that killed at least 250 and left Israelis stunned and reeling.

The Hamas militants broke out of the blockaded Gaza Strip and rampaged through nearby Israeli communities, taking captives, including women, children and the elderly, while Israel's retaliation strikes leveled buildings in Gaza and its prime minister said the country was at war.

Hezbollah struck Israeli positions in a disputed area along the border with Syria's Golan Heights, and Israel's military responded with armed drone strikes on Hezbollah targets in a disputed area where the borders of Israel, Lebanon and Syria meet.

The flare-up on Israel's northern border threatened to draw into the battle a fierce enemy of Israel's which is backed by Iran and estimated to have tens of thousands of rockets at its disposal.

In an assault of startling breadth, Hamas gunmen rolled into as many as 22 locations outside the Gaza Strip early Saturday morning, including towns and other communities as far as 15 miles (24 kilometers) from the Gaza border, while Hamas launched thousands of rockets at Israeli cities. They killed at least 250 people, including 26 soldiers, and took hostages as Israel's military scrambled to muster a response.

On Sunday, the Israeli military said it forces were fighting Hamas incursions in eight places. An Israeli military spokesperson said that two hostage situations had been “resolved,” but did not say whether all the hostages had been rescued alive.

Israel struck 426 targets in Gaza, its miltary said, flattening residential buildings in giant explosions. That included 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.

At least 256 people in the Gaza Strip were killed in Israeli strikes, including 20 children, and close to 1,800 wounded, the Palestinian Health Ministry said.

Israeli media, citing rescue service officials, said at least 250 people were killed and 1,500 wounded in Saturday's attack, making it the deadliest in Israel in decades. Hamas fighters took an unknown number of civilians and soldiers captive into Gaza.

The conflict threatened to escalate with Israel's vows of retaliation, and attacks by Hezbollah.

Hezbollah fired dozens of rockets and shells on Sunday at three Israeli positions in a disputed area along the country's border with Syria's Israeli-occupied Golan Heights.

Israel and Hezbollah are archenemies and have fought several wars in the past, the most recent a 34-day conflict in 2006 that left 1,200 dead in Lebanon and 160 in Israeli. Tensions have been simmering along Israel's northern border for months.

Hezbollah said in a statement that the attack using “large numbers of rockets and shells” was in solidarity with the “Palestinian resistance.” It said the Israeli positions were directly hit.

Israel's military fired back using armed drones at the Lebanese areas.

By attacking Israeli positions in a disputed area rather than Israel proper, Hezbollah appears to be trying to avoid an all-out conflict with Israel.

In a televised address Saturday night, Israeli Prime Minister Benjamin Netanyahu said the military will use all of its strength to destroy Hamas' capabilities. “All the places that Hamas hides in, operates from, we will turn them into ruins,” he added.

“Get out of there now,” he told Gaza residents, who have no way to leave the tiny, overcrowded Mediterranean territory.

Overnight, the Israeli military issued warnings in Arabic to communities near the border with Israel to leave their homes for areas deeper inside the tiny enclave.

Gaza's 2.3 million people have endured a border blockade, enforced to varying degrees by Israel and Egypt, since Hamas militants seized control in 2007.

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.

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

In an amateur video, hundreds of terrified young people who had been dancing at a rave fled for their lives after Hamas militants entered the area and began firing at them.

Among those killed Saturday was Col. Jonathan Steinberg, a senior officer who commanded the Israeli military's Nahal Brigade, a prominent infantry unit.

Before daybreak Sunday, militants fired more rockets from Gaza, hitting a hospital in the Israeli coastal town of Ashkelon, said senior hospital official Tal Bergman. Video provided by Barzilai Medical Center showed a large hole punched into a wall and chunks of debris scattered on the ground of what appeared to be an empty room and a hallway. The military said patients had been evacuated from Barzilai before the strike.

School was canceled across Israel.

Around 3 a.m., a loudspeaker atop a mosque in Gaza City blared a stark warning to residents of nearby apartment buildings: Evacuate immediately. Just minutes later, an Israeli airstrike reduced one nearby five-story building to ashes.

After one Israeli strike, a Hamas rocket barrage hit four cities, including Tel Aviv and a nearby suburb. Throughout the day, Hamas fired more than 3,500 rockets, the Israeli military said.

The shadowy leader of Hamas' military wing, Mohammed Deif, said the assault was in response to the 16-year blockade of Gaza, and a series of recent incidents that have brought Israeli-Palestinian tensions to a fever pitch.

Over the past year, Israel's far-right government has ramped up settlement construction in the occupied West Bank, Israeli settler violence has displaced hundreds of Palestinians there, and tensions have flared around the Al-Aqsa mosque, a flashpoint Jerusalem holy site.

“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.

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.

Comparisons to one of the most traumatic moments in Israeli history sharpened criticism of Netanyahu and his far-right allies, who had campaigned on more aggressive action against threats from Gaza. Political commentators lambasted the government and military over its failure to anticipate what appeared to be a Hamas attack unseen in its level of planning and coordination.

Asked by reporters how Hamas had managed to catch the army off guard, Lt. Col. Richard Hecht, an Israeli army spokesman, replied, “That's a good question.”

The abduction of Israeli civilians and soldiers also raised a particularly thorny issue for Israel, which has a history of making heavily lopsided exchanges to bring captive Israelis home. Israel is holding thousands of Palestinians in its prisons. Hecht confirmed that a “substantial” number of Israelis were abducted Saturday.

Associated Press photos showed an elderly Israeli woman being brought into Gaza on a golf cart by Hamas gunmen and another woman squeezed between two fighters on a motorcycle. AP journalists saw four people taken from the kibbutz of Kfar Azza, including two women.

In Gaza, a black jeep pulled to a stop and, when the rear door opened, a young woman stumbled out, bleeding from the head and with her hands tied behind her back. A man waving a gun in the air grabbed her by the hair and pushed her into the vehicle's back seat.

Thailand's government said that two of its citizens may have been abducted, though the Israeli government could not immediately confirm the details.

Thousands of Thai citizens work in Israel, many of them in the agriculture sector. Israeli TV reported that workers from the Philippines were also among the captives.

Thai Prime Minister Srettha Thavisin has put the country's air force on standby to evacuate its citizens if needed. The Philippine government said it was still working to verify the reports.

A major question now was whether Israel will launch a ground assault into Gaza, a move that in the past has brought intensified casualties. Netanyahu vowed that Hamas “will pay an unprecedented price.” But, he warned, “This war will take time. It will be difficult.”

Israel's military was bringing four divisions of troops as well as tanks to the Gaza border, joining 31 battalions already in the area, a spokesperson said.

Hamas said it had planned for a potentially long fight. “We are prepared for all options, including all-out war,” the deputy head of the Hamas political bureau, Saleh al-Arouri, told Al-Jazeera TV. “We are ready to do whatever is necessary for the dignity and freedom of our people.”

In Gaza, much of the population was thrown into darkness after nightfall as electrical supplies from Israel — which supplies almost all the territories' power — were cut off. Netanyahu's office said in a statement that Israel would stop supplying electricity, fuel and goods to Gaza.

U.S. President Joe Biden said from the White House that he had spoken with Netanyahu to say the United States “stands with the people of Israel in the face of these terrorist assaults. Israel has the right to defend itself and its people, full stop."

Saudi Arabia, which has been in talks with the U.S. about normalizing relations with Israel, called on both sides to exercise restraint. The kingdom said it had repeatedly warned about the danger of “the situation exploding as a result of the continued occupation (and) the Palestinian people being deprived of their legitimate rights.”

The attack comes at a time of historic division within Israel over Netanyahu's proposal to overhaul the judiciary. Mass protests over the plan have sent hundreds of thousands of Israeli demonstrators into the streets and prompted hundreds of military reservists to avoid volunteer duty — turmoil that has raised fears over the military's battlefield readiness.

Palestinians demonstrated in towns and cities around the West Bank on Saturday night. Palestinian health officials said Israeli fire killed five there, but gave few details.