Israel army says it is ready for any scenario as assassination of Hamas leader raises fears of wider Gaza war

Deputy Hamas chief Saleh al-Arouri killed in targeted drone strike in Lebanon

Israel's army says it is prepared for any scenario after the assassination of the deputy leader of Hamas in a strike in Beirut – a killing which has stoked fear of an escalation of the war in Gaza.

While Israel has not claimed responsibility for the drone attack that killed Saleh al-Arouri it called it a "surgical strike against the Hamas leadership". The assassination is a further sign that the nearly three-month war between Israel and Hamas is spreading across the region, drawing in the occupied West Bank, Hezbollah forces on the Lebanon-Israel border, and even Red Sea shipping lanes with container ships between targeting by the Yemen-based Houthis.

Arouri, 57, is the first senior Hamas political leader to be assassinated since Israel began its offensive against Hamas in response to a deadly rampage into Israeli towns on 7 October that killed 1,200 people and saw another 240 people taken hostage. Hamas ally Hezbollah said it was an assault on Lebanese sovereignty.

The Iran-backed, heavily-armed Hezbollah has been exchanging near-daily fire with Israel across Lebanon's southern border since the Gaza war began. More than 100 Hezbollah fighters and two dozen civilians have been killed on Lebanese territory, as well as at least nine Israeli soldiers in Israel. Hezbollah is the largest political and military force in Lebanon and has ministers in the country's government, with fears that a response to the killing of al-Arouri could push Israel's war in Gaza into a wider regional conflict.

"The IDF [Israeli Defence Forces] is in a very high state of readiness in all arenas, in defence and offence," spokesman Rear Adm Daniel Hagari told a briefing. "The most important thing to say tonight is that we are focused and remain focused on fighting Hamas," he added. Israel had long accused al-Arouri of orchestrating attacks on its citizens

Israeli government adviser Mark Regev also stopped short of confirming Israel had carried out the attack, but he told MSNBC: "Whoever did it, it must be clear that this was not an attack on the Lebanese state.

"It was not an attack even on Hezbollah, the terrorist organisation... Whoever did this did a surgical strike against the Hamas leadership. Whoever did this has a gripe with Hamas. That is very clear."

Hezbollah says it has its "finger on the trigger" in response to the killing of al-Arouri. Hezbollah chief Sayyed Hassan Nasrallah is due to make a speech in Beirut on Wednesday afternoon. Previously he had warned Israel against carrying out assassinations on Lebanese soil, vowing a "severe reaction". However, Hezbollah has so far steered clear of increasing its clashes with Israel on the Lebanese border, despite the increasing death toll inside Gaza.

Since the Hamas attack on 7 October Israeli bombardments have laid waste to much of Gaza. Health officials in the Hamas-run territory say more than 22,000 people have killed. Gaza's 2.3 million residents are also engulfed in a humanitarian disaster in which thousands have been left destitute, crammed into shrinking areas in the hope they are safe and threatened by famine due to a lack of food supplies.

Hundreds of Palestinians took to the streets of Ramallah and other towns in the occupied West Bank to condemn al-Arouri's killing, chanting, "Revenge, revenge".

Iranian foreign ministry spokesman Nasser Kanaani said al-Arouri's killing would "ignite another surge in the veins of resistance and the motivation to fight against the Zionist occupiers..."

Shortly before al-Arouri's killing, Hamas' paramount leader Ismail Haniyeh, who is also based outside Gaza, said the movement had delivered its response to an Egyptian-Qatari ceasefire proposal for Gaza.

He reiterated that Hamas' conditions entailed "a complete cessation" of Israel's offensive in exchange for further releases of hostages.

Following al-Arouri's killing, the UN peacekeeping mission in Lebanon has said it us deeply concerned about the possibility of an escalation "that could have devastating consequences for people on both sides of the border".

Reuters and Associated Press contributed to this report