BEIRUT >> The leader of the Lebanese militia Hezbollah said Friday that his group must retaliate after a presumed Israeli strike hit a Beirut neighborhood this week, killing a senior Hamas official, or else all of Lebanon would be vulnerable to Israeli attack.

Hassan Nasrallah appeared to be making the case for a response to the Lebanese public, even at the risk of escalating the fighting between Hezbollah and Israel. But he gave no indication of how or when the militants would act.

The strike that killed Hamas’ deputy political leader, Saleh Arouri, threatened months of efforts by the United States to prevent the war in Gaza from spiraling into a regional conflict.

Nasrallah said it was the first strike by Israel in the Lebanese capital since 2006.

“We cannot keep silent about a violation of this seriousness,” he said, “because this means that all of our people will be exposed (to targeting). All of our cities, villages and public figures will be exposed.”

The repercussions of silence are “far greater” than the risks of retaliating, he added.

Tensions are rising on multiple fronts as U.S. Secretary of State Antony Blinken arrives in the region. Iraqis are furious after an American airstrike killed a militia leader in Baghdad. At the same time, the U.S. is struggling to deter attacks by Yemen’s Iran-backed Houthi rebels on commercial Red Sea shipping.

In Gaza, Israel is moving to scale down its military assault in the north of the territory and pressing its heavy offensive in the south, vowing to crush Hamas. In the south, most of Gaza’s 2.3 million Palestinians are being squeezed into smaller areas in a humanitarian disaster, while still being pounded by Israeli airstrikes.

Since the start of the Gaza war, Hezbollah has fired rockets and missiles into northern Israel, bringing a return bombardment from Israel in near daily cross-border exchanges. After the strike Tuesday in Beirut, the Lebanon-Israel front appeared to be at a critical juncture, with the potential to veer into an all-out war.

On Friday, Israeli aircraft, tanks and artillery struck several areas in Lebanon after rockets and missiles were fired toward Israel, the military said.

But Hezbollah has held back from a dramatic escalation, wary of a repeat of the two sides’ 2006 war in which Israeli bombardment wreaked extensive destruction in Lebanon.

Nasrallah said Friday that the details of Hezbollah’s response “will be decided on the battlefield.” He did not elaborate.

The Beirut strike is not the only thing threatening a wider fight between Israel and Lebanon.

Israeli officials have threatened greater military action against Hezbollah unless it withdraws it fighters from Lebanese territory near their shared border.

A pullback — called for under a 2006 U.N. truce but never implemented — is necessary to stop barrages and allow the return of tens of thousands of Israelis to homes they evacuated near the border, Israel says.

Nasrallah boasted about the evacuations, saying that after Israel forced Lebanese to flee in past conflicts, Hezbollah had now done the same to Israelis, putting political pressure on the government.

Hezbollah’s cross-border attacks aim to engage Israeli forces away from Gaza, Nasrallah said, and the only way to stop them is “to stop the aggression on Gaza.”

Israel says it aims to destroy Hamas’ military capabilities and remove it from power in Gaza after the militants’ Oct. 7 attack on southern Israel, in which they killed around 1,200 people, mainly civilians, and abducted around 250 others.

The army’s chief spokesperson, Rear Adm. Daniel Hagari, said Friday the military plans an investigation into failures connected with the Hamas attack, which generated heavy criticism of military, intelligence and political leaders for being caught off guard. Prime Minister Benjamin Netanyahu has insisted the government must focus on the war first and answer questions later.

Israel’s onslaught in Gaza has killed more than 22,600 people, more than two-thirds of them women and children, according to the territory’s Health Ministry. The ministry’s count does not differentiate between civilians and combatants.

Much of northern Gaza — the most urbanized part of the tiny territory — has been flattened by bombardment and fighting. Most of its population has fled south, joining its residents who have largely been driven from their homes as well. The risk of famine is increasing daily, according to the U.N. humanitarian office, known by the acronym OCHA.

The ground offensive threatens to bring further destruction in the south, particularly in the main battleground city Khan Younis.

Footage aired on Al Jazeera TV showed devastation in downtown Khan Younis. No building in the city’s central Sunneya Square has been left untouched. Some structures have been leveled, while others have been partially destroyed or scorched.

Almost every day this week, strikes have hit in and around Khan Younis’ Al Amal Hospital and a hospital run by the Palestinian Red Crescent, killing dozens of people, the OCHA said.

Martin Griffiths, the U.N. humanitarian chief, said in a statement Friday that the humanitarian community is facing an “impossible mission” of supporting more than 2 million people in Gaza while aid workers are killed, communications blackouts continue, roads are damaged and truck convoys carrying vital supplies shot at. Gaza’s handful of partially functioning hospitals are overwhelmed and infectious diseases are spreading, he said.

Israeli bombardment continued around the territory. At least 13 people were killed when an apartment building was leveled in Maghazi refugee camp in central Gaza, hospital officials said.

In Rafah, at Gaza’s southernmost end, relatives and friends wept over the bodies of six people killed in a strike on a house overnight, including three children.

Sohad al-Derbashi, whose sister was killed in the strike, said the owner of the house had evacuated, fearing he would be targeted since he works as a civil servant in Gaza’s Hamas-led administration, as do thousands of others in the territory. When he came to visit the house last night, the strike hit, she said. Her sister, living on the floor below, was crushed.

“They were civilians, innocent people, with no connection to anything. Even the target who was with Hamas was a civil employee. What did he do wrong?” el-Derbashi said.

Shurafa reported from Deir al-Balah, Gaza Strip, and Jobain from Rafah, Gaza Strip. Associated Press Writer Abby Sewell in Beirut contributed to this report.