Israel carried out a strike in Tyre, south Lebanon, on Saturday, killing one and wounding seven people and endangering the shaky truce that ended a year-long conflict against Hezbollah, as 40 survivors of Hamas captivity called on the Israeli government to halt the “endless war”.

The strike on a building came after Israel carried out dozens of airstrikes in Lebanon on Saturday, its most intense aerial assault on the country in four months. In total, six people were killed, including a child, and 28 injured, according to Lebanon’s health ministry.

In Gaza, Hamas and Palestinian media said on Sunday that an Israeli airstrike in Khan Younis killed Salah al-Bardaweel, a Hamas political leader. Pro-Hamas media said the airstrike killed Bardaweel, a member of its political office, and his wife. Israeli officials had no immediate comment.

Israel’s Lebanon strikes were its deadliest there since the 27 November ceasefire which had put an end to 13 months of hostilities between Hezbollah and Israel. The strike on Tyre, in particular, one of the largest cities in south Lebanon and far from the Lebanese border, was a major escalation and threatened to upend the fragile ceasefire agreement.

An Israeli military spokesperson said it had targeted “attack command headquarters, terrorist operatives, missile launchers, and a weapons depot of the terrorist Hezbollah”.

The wave of Israeli airstrikes was triggered by the launching of three rockets from Lebanon by unknown groups, which were intercepted by the Israeli air force.

In a statement on Saturday afternoon, Hezbollah denied any involvement in the rocket attacks and stressed its commitment to the ceasefire agreement. It added that Israeli claims that it was behind the strikes were “merely a pretext for continued attacks on Lebanon”.

A variety of Palestinian factions, as well as other armed groups, operate in southern Lebanon and not all are under Hezbollah’s command. Both the Israeli military and the Lebanese Ministry of Defence said it was investigating who could have fired the rockets.

The Lebanese army said it found and dismantled what it called three “primitive rocket launchers” in south Lebanon after the rocket fire towards Israel. Pictures released by the army showed fragments of bombs and three wooden posts dug into the earth, seemingly used in the launching of the rockets.

Lebanon’s minister of defence, Michel Menassa, said the country was “continuing its diplomatic, political and military efforts to ensure Lebanon’s sovereignty”.

The Israeli defence minister, Israel Katz, warned of a severe response to the rocket fire, which was shot at the Israeli border village of Metula.

“Metula and Beirut will be treated the same. The Lebanese government is fully responsible for any fire originating from its territory,” Katz said.

The ceasefire between Israel and Hezbollah has stopped full-scale military hostilities between the two warring parties, though Israel has conducted hundreds of airstrikes on Lebanon despite the truce. Israel has maintained that it reserves the right to unilaterally enforce any violations of the ceasefire in Lebanon and has continued to strike what it says are Hezbollah targets across the country.

Hezbollah launched rockets near an Israeli military post in the week after the establishment of the ceasefire, but otherwise has not attacked Israel since. The group has been severely weakened after its war with Israel, with most of its senior leadership dead, thousands of its fighters killed and its weapons stock depleted.

The Lebanese prime minister, Nawaf Salam, warned on Saturday that renewed military operations in south Lebanon could risk dragging the country back into war and urged the ministry of defence to ensure that the Lebanese state, rather than Hezbollah, decides whether Lebanon goes to war.

Unifil, the UN peacekeeping force that monitors the Israel-Lebanon border, warned against further military escalation that could lead to the ceasefire being broken.

“The situation remains extremely fragile and we encourage both sides to uphold their commitments,” it said in a statement on Saturday.

In Israel, several thousand protesters took to the streets of Tel Aviv and Jerusalem on Saturday, blocking key highways across the country in a demonstration against Netanyahu’s government.

The immediate trigger for the anger was the government’s attempt to dismiss Ronen Bar, the head of the internal security agency, a move described as an attempt to undermine Israel’s democratic system, but the prime minister’s decision to shatter a two-month-old truce in Gaza with waves of lethal airstrikes has also fuelled the demonstrations.

Forty freed hostages of Hamas captivity and 250 family members of Israeli soldiers and civilians still held in Gaza signed a letter on Friday calling on Netanyahu to halt Israel’s renewed military activities and return to the negotiating table in order to secure the release of the remaining 59 hostages who are still in the territory. In a letter sent to the prime minister, they warned that failure to do so would condemn the living hostages to death.

“This letter was written in blood and tears,” the text reads. ‘‘It was drafted by our friends and families whose loved ones were killed and murdered in captivity and who are crying out: ‘Stop the fighting. Return to the negotiating table and fully complete an agreement that will return all of the hostages, even at the cost of ending the war’.”

The signatories attacked the government for “choosing an endless war over saving and returning the hostages, and by doing that, sacrificing them. This is a criminal policy – you do not have a mandate to sacrifice 59 people.’’

The letter comes as Israel’s defence minister on Friday said he had instructed the military to “seize more ground” in Gaza and threatened to annex part of the territory unless Hamas released Israeli hostages still held in the devastated territory.

Israeli officials have escalated their threats in recent days, calling on Palestinians in Gaza to overthrow Hamas or face the consequences.

“I ordered [the army] to seize more territory in Gaza,” Katz said in a statement. “The more Hamas refuses to free the hostages, the more territory it will lose, which will be annexed by Israel.”

Gaza’s civil defence agency said more than 500 people had been killed since the bombardment resumed, one of the highest tolls since the war began more than 17 months ago with Hamas’s attack on Israel.

A three-phase ceasefire was agreed in January but Israel refused to begin talks on the implementation of a second phase, which was supposed to lead to a return of all hostages, the withdrawal of Israeli forces from Gaza and a permanent end to hostilities.

Instead, Israel proposed a new plan, reportedly put forward by the US envoy, Steve Witkoff, involving a 30- to 60-day truce and the release of all remaining hostages. Israel made no mention of releasing more Palestinian prisoners – a key component of the first phase.

On Saturday, the Fatah movement of Palestinian Authority president, Mahmoud Abbas, called on Hamas to relinquish power in order to safeguard the “existence” of Palestinians in the Gaza Strip.

“Hamas must show compassion for Gaza, its children, women and men,” Fatah spokesperson Monther al-Hayek said in a message sent to AFP, urging the militant group to “step aside from governing and fully recognise that the battle ahead will lead to the end of Palestinians’ existence” if it remains in power in Gaza.

Hamas said on Friday it was still debating Witkoff’s proposal and other proposals made by intermediaries, including Egypt.

The intense fighting comes as Netanyahu is locked in a fierce battle with Israel’s judicial system after the supreme court blocked his attempt to fire the head of the Shin Bet domestic intelligence agency, who has been investigating Netanyahu’s close aides for alleged breaches of national security, including leaking classified documents to foreign media, and allegedly taking money from Qatar, which is known to have given significant financial aid to Hamas.

Amid protests against ministers’ vote to sack Bar, the top court on Friday froze the decision, with the order remaining in place until the court can hear petitions filed by the opposition and an NGO against the dismissal.

Netanyahu said in a post on X that “the government of Israel will decide” who headed the domestic security agency, writing: “The State of Israel is a state of law, and according to the law, the government of Israel decides who will be the head of the Shin Bet.”

About 1,200 people, mostly Israeli civilians, died in the surprise attack by Hamas in October 2023. The ensuing Israeli offensive into Gaza has killed more than 49,000 people, mostly civilians.