Rescue workers in Beirut searched on Saturday for people still missing in rubble after an Israeli air strike targeting Hezbollah commanders the previous day killed at least 37 people in a suburb of the Lebanese capital, according to authorities.

Hezbollah said that 16 members, including senior leader Ibrahim Akil and another commander, Ahmed Wahbi, were among those killed in the deadliest strike in nearly a year of conflict with Israel.

Israel's army said it hit an underground gathering of Akil and leaders of Hezbollah's elite Radwan forces, and had almost completely dismantled its military chain of command.

The attack leveled a multi-story residential building in the crowded suburb and damaged a nursery next door, a security source said. Three children and seven women were among those killed, according to Lebanon's Health Ministry.

Cross-border strikes continued on Saturday. Israeli warplanes carried out the heaviest bombardment in 11 months of fighting across Lebanon's south and Hezbollah claimed rocket attacks on military targets in Israel's north.

The Israeli army said it hit around 180 targets, destroying thousands of rocket launch barrels.

Lebanese Prime Minister Najib Mikati cancelled a planned trip to the UN General Assembly in New York. U.S. National Security Advisor Jake Sullivan said he was worried about escalation but that the Israeli killing of a top Hezbollah leader brought justice to the group, which Washington designates as terrorists.

Israel braces for retaliation

Hezbollah has said it will keep fighting Israel until it agrees to a ceasefire in Gaza. U.S. officials say that is unlikely anytime soon. Israel wants Hezbollah to cease fire and withdraw forces from the border region irrespective of any Gaza deal.

Anticipating retaliation, the Israeli military restricted gatherings and raised the alert level for residents of northern communities. The alert went as far south as the coastal city of Haifa, signaling Israel thought Hezbollah could strike deeper than it had since the Gaza conflict began.

In southern Lebanon on Saturday, people described huge explosions that lit up the night sky and shook the ground as Israel carried out its latest strikes.

Lebanon's Minister of Public Works and Transport Ali Hamieh told reporters at the scene of Friday's strike in the Beirut suburb that at least 23 people were still missing.

"The Israeli enemy is taking the region to war," he said.

Defence Minister Yoav Gallant, who said this week Israel was launching a new phase of war on the northern border, posted on X: "The sequence of actions in the new phase will continue until our goal is achieved: the safe return of the residents of the north to their homes."

Tens of thousands of people have left their homes on both sides of the Israel-Lebanon border since Hezbollah began firing rockets at Israel in October in sympathy with Palestinians in Gaza.

The U.S. State Department said it had renewed its travel advisory for Lebanon, continuing to urge U.S. citizens not to travel there and for those already in the country to depart while commercial options are still available.

Airspace in northern Israel, from the city of Hadera, was closed to private flights but international flights were unaffected, the military said.

With at least 70 people killed in Lebanon this week, the conflict toll in the country since October has surpassed 740 during the worst Israel-Hezbollah flare-up since a 2006 war.

UN Special Coordinator for Lebanon Jeanine-Hennis Plasschaert said on Friday the strike in a densely populated area of Beirut was part of "an extremely dangerous cycle of violence with devastating consequences. This must stop now."

(With input from Reuters)