TEL AVIV, Israel — The Middle East braced for a potential flare-up in violence on Sunday after Israeli authorities said a rocket from Lebanon struck a soccer field in the Israeli-controlled Golan Heights, killing 12 children and teens in what the military called the deadliest attack on civilians since Oct. 7. It raised fears of a broader regional war between Israel and Hezbollah, which in a rare move denied it was responsible.

The White House National Security Council said it had been speaking with Israeli and Lebanese counterparts since the attack and was working on a diplomatic solution to “end all attacks once and for all” in the border area between Israel and Lebanon.

The Israeli military said it struck a number of targets inside Lebanon overnight into Sunday, though their intensity was similar to months of cross-border fighting between Israel and the Iranian-backed Hezbollah. Hezbollah said it also carried out strikes. There were no immediate reports of casualties.

Saturday’s attack came as Israel and Hamas are negotiating a cease-fire proposal to end the nearly 10-month war in Gaza.

Here is a look at the broader repercussions:

What Happened?

On Saturday, a rocket slammed into a soccer field where dozens of children and teens were playing in the Druze town of Majdal Shams, about 12 kilometers (7 miles) south of Lebanon and next to the Syrian border. Twelve were killed and 20 others wounded, according to the Israeli military. One 11-year-old was missing, residents told Israeli media.

“I feel darkness inside and out. Nothing like this happened here,” resident Anan Abu Saleh said. “There’s no way to explain this. I saw children, I don’t want to say what I saw, but it’s horrible, really horrible. We need more security.” On Sunday, the coffins passed through a crowd of thousands.

The Druze are a religious sect that began as an offshoot of Shiite Islam and has communities in Israel, Syria and Lebanon. There are about 25,000 Druze in the Israeli-controlled Golan Heights, according to Yusri Hazran of the Hebrew University.

The Druze are considered among Israel’s most loyal citizens, although those in the Golan Heights have a more fraught relationship with authorities. Israel captured the Golan, a strategic plateau, from Syria in the 1967 Mideast war and annexed it in 1981. Much of the international community considers the area to be occupied territory. While Druze leaders in the Golan profess allegiance to Syria, relations with Israel are normally good.

“Big anger, big, big. I have no feelings that I can explain to you,” said Hassan Shakir, a Majdal Shams resident.

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Could This Mean a Wider War?

Attacks along the Israel-Lebanon border have simmered below the threshold of all-out war since the start of the conflict in Gaza. But the toll and young victims in Saturday’s attack could push Israel to respond more severely.

Israeli Prime Minister Benjamin Netanyahu hurried home from the U.S. after the strike and warned that Hezbollah “will pay a heavy price for this attack, one that it has not paid so far.” He was weighing options Sunday.

U.S. Secretary of State Antony Blinken said Sunday that “every indication” showed the rocket came from Hezbollah. Israeli military’s Chief of Staff Lt. Gen. Herzi Halevi said a Falaq rocket with a 53-kilogram warhead belonging to Hezbollah was fired.

Hezbollah began firing rockets at Israel the day after Hamas’ attack on Oct. 7. Israel responded by targeting what it calls Hezbollah’s military infrastructure with airstrikes and drones. Most attacks have been confined to border areas, though Israel has assassinated Hezbollah and Hamas leadership farther north in Lebanon. Tens of thousands of people along the border have evacuated.

Since early October, Israeli airstrikes in Lebanon have killed more than 500 people, including around 90 civilians. On the Israeli side, 22 soldiers and 24 civilians have been killed.

Hezbollah has far superior firepower than Hamas. Igniting a war in Israel’s north while it’s engaged in Gaza would overburden the military, Barak Ben-Zur, a researcher at the International Institute of Counter-Terrorism, told journalists: “We are not, let’s say, capable to do it in both places and at the same time.”

In Lebanon, some prepared for more fire from Israel. Lebanon’s national airline announced it had postponed the Beirut arrival of seven flights until Monday morning, without saying why. Caretaker Prime Minister Najib Mikati had urgent calls with diplomats and politicians, his office said.

“I doubt that there will be a strike, but nothing is far-fetched when it comes to the enemy,” said Abdallah Dalal, a resident of the Lebanese border village of Chebaa. Israeli officials said the rocket that hit Majdal Shams was fired nearby.

Any conflict could bring in Iran, which warned Israel that a strong reaction to the Golan Heights strike would lead to “unprecedented consequences.” Iran and Israel’s shadow war burst into the open in April, when Iran launched 300 missiles and drones at Israel, most of them intercepted, in response to the killing of an Iranian general.

The United Nations secretary-general called for maximum restraint by all parties.

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Could This Impact the War in Gaza?

An Egyptian official said the attack in the Golan Heights could give urgency to negotiations to reach a cease-fire deal in Gaza.

“Both fronts are connected,” he said. “A cease-fire in Gaza will lead to a cease-fire with Hezbollah.” The official spoke on condition of anonymity because he wasn’t authorized to discuss the sensitive talks with the media.

In a statement, the Egyptian foreign ministry called on all influential international players to “intervene immediately to spare the peoples of the region further disastrous consequences of the expansion of the conflict.”

Officials from the United States, Egypt and Qatar were meeting Sunday with Israeli officials in Rome in the latest push for a deal. The head of Israel’s Mossad spy agency, David Barnea, returned home and negotiations will continue in the coming days, Netanyahu’s office said.