Israel's war on Gaza was facing a heightened risk of spreading into neighboring Lebanon Wednesday with the killing of Hamas deputy leader in Beirut a day earlier.

Israeli forces, in the meantime, intensified their bombing of the Gaza Strip and told civilians to leave a refugee camp in the north of the Palestinian enclave.

It has neither confirmed nor denied that it killed Saleh al-Arouri in a drone strike in the Lebanese capital Tuesday. But military spokesperson Rear Adm. Daniel Hagari said Israeli forces were in a high state of readiness and prepared for any scenario.

The assassination was a further sign that Israel's nearly three-month war on Gaza was spreading across the region, drawing in the occupied West Bank, Hezbollah forces on the Lebanon-Israel border and even Red Sea shipping lanes.

Arouri, 57, who lived in Beirut, was the first senior Hamas political leader to be assassinated since Israel began its offensive against the resistance group in response to a deadly incursion into Israeli towns on Oct. 7.

Hamas politburo member Hossam Badran said in a eulogy for Arouri: "We say to the criminal occupation (Israel) that the battle between us is open."

Israel had long accused him of orchestrating attacks on its citizens. But a Hamas official said he was also "at the heart of negotiations" conducted by Qatar and Egypt over the outcome of the Gaza war and the release of Hamas-held Israeli hostages.

Hezbollah chief Sayyed Hassan Nasrallah was due to speak in Beirut on Wednesday afternoon. Previously he had warned Israel against carrying out assassinations on Lebanese soil, vowing a "severe reaction."

The Hezbollah, a Hamas ally, has been exchanging near-daily fire with Israel across Lebanon's southern border since the Gaza war began.

More than 100 Hezbollah members and two dozen civilians have been killed on Lebanese territory, as well as at least nine Israeli soldiers in Israel.

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

Refugee camp under fire

The Israeli military said in its daily briefing that "intensive battles" with militants were continuing in Gaza on Wednesday in the southern city of Khan Younis. It has said previously it is trying to flush out Hamas leaders in the area.

Residents and Palestinian media said Israeli forces bombed the al-Nuseirat refugee camp in the northern part of the Hamas-ruled enclave overnight and into Wednesday, destroying several multi-floor buildings.

Israeli planes also dropped leaflets on al-Nuseirat ordering people to leave seven districts.

"You are in a dangerous combat area. The IDF is operating heavily in your area of residence. For your safety the IDF urge you to immediately evacuate this area and leave towards the known shelters in Deir Al-Balah (west)," the leaflets said.

Israeli warplanes and tanks also stepped up attacks on the al-Bureij refugee camp.

Hamas' armed members said they had killed 10 Israeli soldiers in fighting in al-Bureij and hit five tanks and troop carriers. The Israeli military said the number of its soldiers killed since its first invasion into Gaza on Oct. 20 had reached 177.

In the al-Maghazi refugee camp, health officials said at least four people were killed in an Israeli airstrike on a house. They said three people were also killed in an air strike on a house in Rafah in the south of Gaza.

Israel says it tries to avoid harm to civilians. But the total recorded Palestinian death toll had reached 22,313 by Wednesday, 128 of them in the past 24 hours, the Gaza health ministry said.

'Veins of resistance'

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

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

Shortly before 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 cease-fire proposal.

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

Israel believes 129 hostages remain in Gaza after some were released during a brief truce in late November and others were killed during airstrikes and rescue or escape attempts.