Israel launched airstrikes on several locations in Lebanon in retaliation for a rocket attack, killing six people in the heaviest exchange of fire since its ceasefire with the militant group Hezbollah began nearly four months ago.

The exchange sparked concern about whether the ceasefire would hold, days after Israel relaunched its war with another Iran-backed militant group, Hamas, in Gaza.

In a statement, Hezbollah denied being responsible for the attack, saying it was committed to the truce.

Israeli Prime Minister Benjamin Netanyahu’s office said it instructed the army to respond forcefully against dozens of targets in Lebanon, where the Iran-backed Hezbollah is based.

Israel’s army said six rockets were fired toward Metula, a town along the border with Lebanon.

Three crossed into Israel and were intercepted.

The army said it “cannot confirm the identity of the organization that fired the rockets.” It said it struck Hezbollah command centers and dozens of rocket launchers.

An Israeli strike on the southern Lebanese village of Touline killed five people, including a child, and wounded 10 others, including two children, Lebanon’s state-run National News Agency reported.

Another Israeli strike on Saturday night hit a garage in the coastal city of Tyre, the NNA reported, with one person killed and seven wounded.

It was the first attack on the city since the ceasefire took effect on November 27. And a strike on Hawsh al-Sayed Ali village along the border with Syria wounded five people, according to the NNA.

In a statement, Lebanon’s prime minister, Nawaf Salam, asked the country’s military to take all necessary measures in the south, but said the country does not want to return to war.

Hezbollah began launching rockets, drones and missiles into Israel the day after Hamas’ on October 7, 2023, attack out of Gaza ignited the war there.

The Israel-Hezbollah conflict boiled over into all-out war in September as Israel carried out waves of airstrikes and killed most of the militant group’s senior leaders.

The fighting killed over 4,000 people in Lebanon and displaced about 60,000 Israelis.

Israeli forces were supposed to withdraw from all Lebanese territory by late January under the ceasefire deal.

The deadline was extended to February 18, but Israel has remained in five locations in Lebanon across from communities in northern Israel.

Meanwhile, Israel has carried out dozens of airstrikes on southern and eastern Lebanon, saying it attacked Hezbollah, while continuing drone attacks that have killed several members of the militant group.

Lebanon has appealed to the U.N. to pressure Israel to fully withdraw. The United Nations Interim Force in Lebanon said it was alarmed at the possible escalation of violence and urged all parties to avoid jeopardising the progress made.

Israeli airstrikes pound Gaza

The strikes came a day after Israel said it would carry out operations in Gaza “with increasing intensity” until Hamas frees the 59 hostages it holds – 24 of whom are believed to be alive.

Israeli strikes on Friday night killed at least nine people, including three children, in a house in Gaza City, according to Al-Ahli Hospital, which received the bodies.

“Rubble and glass started falling on us,” said Sameh al-Mashharawi, who lost his brother in the attack.

He mourned with his young nephew Samir al-Mashharawi, whose parents and siblings were killed.

The 12-year-old, his head and wrists bandaged, sat in the back of a truck and cried.

Israel’s military said Friday that its forces were planning fresh assaults into three neighborhoods west of Gaza City and issued warnings on social media for Palestinians to evacuate the areas.

“Hamas, unfortunately, understands military pressure,” Netanyahu’s foreign policy advisor Ophir Falk told The Associated Press.

Around 600 Palestinians have been killed since Israel relaunched the war on Tuesday.

Israel had already cut off the supply of food, fuel, and humanitarian aid to Gaza’s roughly 2 million Palestinians, aiming to pressure Hamas over ceasefire negotiations.

The international community has condemned the resumed attacks.

The initial 2023 attack by Hamas-led militants killed some 1,200 people, mostly civilians, and took 251 hostages.

Most of the hostages have been freed in ceasefire agreements or other deals. Israeli forces have rescued eight living hostages and recovered the bodies of dozens more.

Israel’s retaliatory offensive has killed more than 49,000 Palestinians, according to Gaza’s Health Ministry.

It does not say how many were militants but says more than half of those killed were women and children. Israel says it has killed around 20,000 militants, without providing evidence.

Uproar over Shin Bet chief

Tens of thousands of Israelis on Saturday again protested the government’s failure to negotiate a hostage deal and its move to fire the head of the country’s Shin Bet internal security service.

They called for new elections.

The Supreme Court has ordered a temporary halt to Ronen Bar’s dismissal until an appeal is heard.

Israel’s attorney general has ruled that the Cabinet has no legal basis to dismiss him.

Netanyahu said in a statement late Saturday that Bar “will not remain the head of the Shin Bet” and “Israel will remain a democratic state.”

He argued that his loss of confidence in Bar long predates the Shin Bet investigation into illicit ties between several of his aides and Qatar.

Opposition leader Yair Lapid called for a tax rebellion and general strike if the government defies the court ruling, saying: “If this happens, the entire country needs to grind to a halt.”