The Lebanese militant group Hezbollah declared on Monday that it would not lay down its weapons, a day after the authorities in Lebanon said 14 people were killed in Israeli attacks on Sunday, one of the deadliest days since a truce was declared this month.

Naim Qassem, the leader of Hezbollah, an Iranian-backed group, said in a written statement that it would not “relinquish its weapons or its defenses.” Israel has demanded Hezbollah’s disarmament as a precondition for ending its invasion of southern Lebanon.

But it is still far from clear whether the Lebanese government can rein in Hezbollah, whose devoted Shiite Muslim supporters and battalions of fighters have long made it Lebanon’s dominant military power.

In another sign of strains on the truce, the Israeli military said on Monday that it had attacked the Bekaa Valley in eastern Lebanon. Those strikes were some of the deepest since President Trump declared a cease-fire in the country earlier this month.

The latest war in Lebanon began in early March when Hezbollah attacked Israel after the United States and Israel launched a war on its patron, Iran.

Analysts say the truce, brokered by the United States, was more of a de-escalation than a true end to hostilities.

Israel and Hezbollah have continued to trade attacks almost daily, although the fighting has mostly been confined to southern Lebanon. Israeli forces are razing Lebanese border towns there, part of an effort that could lay the groundwork for a longer occupation in southern Lebanon.

Hezbollah has also fired rockets and explosive drones at Israeli communities, as well as at invading Israeli forces. On Sunday, the Israeli military said a soldier had been killed in Lebanon, raising the death toll in Israel’s ranks in the current conflict to at least 16.

Lebanon’s Health Ministry said the 14 people killed in the Israeli attacks on Sunday included two women and two children, but did not give many other details, state media reported. More than 2,500 people in Lebanon have been killed since the latest war erupted in early March, according to the ministry.

Benjamin Netanyahu, the Israeli prime minister, accused Hezbollah on Sunday of “essentially disintegrating the cease-fire.” But while Israel has repeatedly bombarded south Lebanon, it has refrained from attacking Beirut, the Lebanese capital.

Were Israel to buck the truce entirely, it could run afoul of Mr. Trump, who personally announced the agreement and says he wants to invite both Mr. Netanyahu and Joseph Aoun, the Lebanese president, to Washington for further talks.

Lebanese and Israeli officials have already met twice to discuss next steps, most recently at the White House. The negotiations broke a long-held taboo on direct negotiations between the two countries.

Mr. Qassem condemned the Lebanese government for negotiating with Israel, adding that the country’s leaders had made a “gratuitous and humiliating concession” by even sitting down with Israeli officials.

In November 2024, a similar cease-fire, mediated by the Biden administration, ended a year of full-blown war between Israel and Hezbollah. But both countries accused one another of violating their commitments under the truce.

Israel attacked in Lebanon on a near-daily basis, including in Beirut, leading many Lebanese to wonder whether the truce existed except on paper. Israeli leaders accused Lebanon of failing to uphold its own commitment to crack down on Hezbollah.

Rawan Sheikh Ahmad contributed reporting.