Israel declared a 48-hour state of emergency after carrying out a pre-emptive attack on Hezbollah sites in southern Lebanon as the Iran-backed militant group began what it said was its initial response to last month’s killing of its military chief by Israel.

The Israeli military said it sent 100 warplanes over Lebanon and took out thousands of rocket launchers aimed at targets in northern and central Israel. Lieutenant Colonel Nadav Shoshani, a military spokesman, said Hezbollah then fired hundreds of missiles and rockets at Israel.

He said the damage to Israel from those projectiles appeared to be very limited and that Israel’s operation in Lebanon was essentially over for now, although both sides remain on high alert with occasional firing. Hezbollah also said its operation on Sunday had concluded.

Israel’s main airport outside Tel Aviv was shut down for a few hours, with incoming flights directed toward neighboring states. Shoshani said this was because of concern that missiles were aimed at the center of the country, but Israel’s actions ended that risk for now.

Although Sunday’s attacks remained within the so-called rules of engagement, they raise concerns that the near-daily trading of fire between Israel and Hezbollah for the past 10 months could at any moment escalate into a wider war.

Hezbollah said its attack on Israel was the start of retaliation for the killing of its commander on July 30 in Beirut’s southern suburbs. The group said it fired more than 320 missiles, followed up by drones, to target 11 army barracks and military sites in northern Israel.

Israel hasn’t confirmed the targets but sirens sounded repeatedly in the north on Sunday morning. The military there is limiting gatherings to 300 people inside and 30 people outside. It said workplaces can operate normally if they’re inside and have bomb shelters that can be reached quickly.

A Lebanese group allied with Hezbollah said one of its fighters was killed in Sunday’s airstrikes. Two other people were killed and several others were wounded, according to state-run National News Agency.

Shoshani said Israel saw Hezbollah preparing to fire missiles and rockets and acted pre-emptively. Israel warned Lebanese civilians in the areas where Hezbollah operates to move out of harm’s way, he said. The Israeli action was limited to southern Lebanon.

Israeli Prime Minister Benjamin Netanyahu convened a security cabinet meeting and said he was “determined to do everything to defend our country, to return the residents of the north securely to their homes, and to continue upholding a simple rule: Whoever harms us – we will harm them.”

The government’s delegation to talks aimed at reaching a cease-fire in Gaza was due to leave for Cairo on Sunday as planned, suggesting that those negotiations will resume. Hamas said Saturday it was sending a team to meet with mediators.

Pentagon spokesman Pat Ryder said that “We continue to closely monitor the situation and have been very clear that the US is postured to support the defense of Israel.” He referred questions about it to the Israelis.

Shoshani noted that Israeli Defense Minister Yoav Gallant and US Defense Secretary Lloyd Austin spoke by phone over the weekend and that a top US commander in the region had visited twice recently. He declined to say whether the US was given advance warning of Sunday’s attack, adding, “This was an Israeli operation.”

Israel and Hezbollah have been trading fire along the border since October, when the Lebanese organization entered the fray in support of the Palestinian group Hamas in Gaza. Israeli strikes have killed at least 500 people since then, most of them Hezbollah fighters. In Israel, roughly 30 soldiers and 18 civilians have been killed by Hezbollah attacks.

Preventing the skirmishes escalating even further has been at the heart of international diplomatic efforts to ease tension across the Middle East.

On July 30, an Israeli airstrike killed Hezbollah’s military chief Fuad Shukr in Beirut. Hours later, Iran blamed the Jewish state for killing the head of Hamas’ political office Ismail Haniyeh in Tehran. Iran has vowed to retaliate.

The US has been trying to mediate between Lebanon and Israel to reach a compromise over border disputes. Israel wants Hezbollah to move its fighters away from the border to allow its citizens to return to the north. Tens of thousands of Israelis and Lebanese have been evacuated from the border area due to the fighting.

Hezbollah, which is backed by Iran and designated a terrorist organization by the US, says it will continue hostilities with Israel until the country agrees a cease-fire with Hamas in Gaza.

The war in the Palestinian enclave began on Oct. 7 after Hamas militants, also supported by Iran, invaded Israel and killed 1,200 people and abducted others. Israel’s retaliation in Gaza has killed at least 40,000 people, according to health officials in Gaza, which is ruled by Hamas.