Israel launched strikes into southern Lebanon on Monday against Hezbollah, the Iranian-backed militia, which said one of its senior commanders had been killed there, adding to concerns that Israel’s fight against Hamas in Gaza could erupt into a wider regional war.

Hezbollah and Israel have shelled and fired rockets at each other frequently over the past three months, in some of the most intense fighting along the Lebanese border since Israel and Hezbollah were at war in 2006.

The killing of the commander came amid Secretary of State Antony J. Blinken’s latest trip to the Middle East, part of the Biden administration’s efforts to prevent the Israel-Hamas war from spreading to other fronts, and as Israeli officials issued new warnings to their adversaries.

During a visit to northern Israel on Monday, Prime Minister Benjamin Netanyahu told soldiers guarding the border that Israel was ready “to do whatever is necessary to restore security to the north.”

“Hezbollah got us wrong in a major way in 2006, and is getting us seriously wrong even now,” he said, referring to Israel’s last war with Hezbollah, according to a statement by his office.

Concerns over a wider war have preoccupied the United States and its allies since the Oct. 7 Hamas-led attacks in Israel that killed about 1,200 Israelis and sparked the war in Gaza. Those concerns largely center on three Iranian-backed groups — Hezbollah in Lebanon; the militias in Iraq and Syria; and the Houthis in Yemen, who have launched attacks on commercial ships in the Red Sea and prompted the United States to dispatch two aircraft carriers to the Eastern Mediterranean in October.

During a visit to Saudi Arabia on Monday, Mr. Blinken met briefly with Josep Borrell, the European Union’s top diplomat, to “discuss efforts to prevent the conflict from spreading and secure a lasting peace for the region,” according to a spokesman, Matthew Miller. Like Mr. Blinken, Mr. Borrell was in Saudi Arabia to meet with the kingdom’s de facto ruler, Crown Prince Mohammed bin Salman.

“The Israelis have been very clear with us that they want to find a diplomatic way forward, a diplomatic way forward that creates the kind of security that allows Israelis to return home — nearly 100,000 Israelis have been forced to leave their homes in northern Israel because of the threat coming from Hezbollah and Lebanon — but also allows Lebanese to return to their homes in southern Lebanon,” Mr. Blinken said in Saudi Arabia, before flying to Tel Aviv. “And we’re working intensely on that effort, and doing so diplomatically.”

The clashes along the Israeli border with Lebanon have elicited repeated Israeli warnings of more aggressive military action. More than 130 Hezbollah fighters have been killed in the clashes, according to the Reuters news agency.

The Biden administration has been calling for an agreement that would move Hezbollah forces away from the border, but with little apparent progress. Although Israeli officials have said that time for a diplomatic deal is running out, analysts say that Israel is wary of significantly expanding the conflict with Hezbollah while the military is still engaged in intensive fighting in Gaza.

But Lebanese officials have attributed strikes far past the border to Israel, including one last week near Beirut that killed a top Hamas official who was a liaison to Hezbollah.

Hezbollah identified the commander killed on Monday as Wissam Hassan al-Tawil. A Lebanese security official, speaking on condition of anonymity because of the sensitivity of the matter, said that he had been part of the Radwan unit, which Israel says aims to infiltrate its northern border. The official said that Mr. al-Tawil had been killed in an Israeli strike in Khirbet Selm, a village in southern Lebanon that is about nine miles from the Israeli border.

The Radwan unit has taken the lead in Hezbollah’s long-running conflict with Israel and in the cross-border attacks that have escalated in the three months that Israel and Hamas have been at war. Israeli military analysts say that Radwan has adopted the mission of conquering the northern Israeli region of Galilee.

The origins and makeup of the unit are murky. The group took its name from the nom de guerre of its former leader, Imad Mughniyeh, who was assassinated in Syria in 2008.

Mr. al-Tawil’s role in Hezbollah was not immediately clear. But in an apparent effort to signal his seniority, Al Manar, a Hezbollah-owned Lebanese broadcaster, posted images of him alongside various high-ranking Hezbollah officials including the group’s leader, Hassan Nasrallah, as well Qassim Suleimani, the Iranian general who was killed in a U.S. drone strike in 2020.

The Israeli military did not directly comment on the Monday attack. In a statement, it said that an Israeli fighter jet had carried out “a series of strikes,” hitting a Hezbollah military site, without giving further details.

A day earlier, the Israeli military said that it had killed at least seven members of Hezbollah in strikes aimed at destroying the Radwan unit and that it was ready to attack more of Hezbollah’s positions. The Israeli military’s chief of staff, Lt. Gen. Herzl Halevi, said that its forces were determined to keep the pressure on Hezbollah and that if those efforts fell short, Israel was ready to fight “another war.”

“We will create a completely different reality, or we will get to another war,” he said on Sunday.

Hezbollah attacks damaged an Israeli military base on Saturday, one of the group’s biggest assaults against Israel in months of back-and-forth strikes. The powerful Lebanese militia has pledged support for Hamas, and in recent days, it has stepped up assaults on Israel in response to the killing last week of Saleh al-Arouri, a senior Hamas leader, outside Beirut.

The rocket fire on the Israeli base, the Northern Air Control Unit on Mount Meron, caused significant damage, according to accounts in the Israeli news media. But the base is still operating “and has been reinforced with additional systems,” Rear Adm. Daniel Hagari, the Israeli military’s chief spokesman, said on Sunday.

Israeli leaders have repeatedly declared in recent weeks that there are only two options for restoring calm in the conflict with Hezbollah: a diplomatic solution that would move the Radwan forces farther from the border, north of the Litani River; or, failing that, a major Israeli military offensive aimed at achieving the same goal.

“Hezbollah is dragging Lebanon into a totally unnecessary war,” Eylon Levy, an Israeli government spokesman, told reporters on Monday.

“We are now at a fork in the road,” he added. “Either Hezbollah backs off, hopefully as part of a diplomatic solution, or we will push it away.”

Calm, Israeli officials say, is a prerequisite to allow about 80,000 Israelis who have been evacuated from the area near the border with Lebanon to return to their homes. A similar number of Lebanese have fled their homes on the other side.

Edward Wong contributed reporting from Al Ula, Saudi Arabia.