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The Israeli military on Monday said a field commander in Hezbollah's elite Radwan Force was among three members of the Lebanese group killed in a strike on southern Lebanon.
Ali Ahmad Hussein was responsible for the planning and execution of several attacks on Israel, the military added.
Iran-backed Hezbollah, a powerful Lebanese militia and political party, announced his death in a statement without indicating his rank or where he died.
Israeli forces released footage of fighter jets bombing a building where the three Hezbollah members were believed to have been.
Several people were injured in the strike, which caused “severe damage to property and homes adjacent to the targeted house, which is located in a residential area”, Lebanon's state-owned news agency reported.
It said more than 10 families lost their homes in the attack.
The Radwan Force is Hezbollah's secretive special operations unit. It is named after Imad Mughniyeh, a former military commander with the group, who went by the name Hajj Radwan. He was assassinated in 2008 in a joint Israeli-US operation.
In January, an Israeli strike killed senior Hezbollah and Radwan commander Wissam Tawil.
Hezbollah and Israel have been engaged in almost daily cross-border fire since October 8, with the violence increasing fears of all-out war. Hezbollah has said it is carrying out attacks in support of Hamas in the Gaza Strip.
On Monday, UN officials called for de-escalation “while there is still space for diplomacy”.
“It is six months since the exchanges of fire across the Blue Line began, and continue unabated, taking a heavy toll on both sides,” said a joint statement from UN special co-ordinator for Lebanon, Joanna Wronecka, and Aroldo Lazaro Saenz, head of the UN Interim Force in Lebanon.
Unifil guards the Blue Line between Lebanon and Israel, a UN demarcation created after the withdrawal of Israeli troops from southern Lebanon in 2000.
“The violence and suffering has gone on too long. It must stop,” the officials said.
Hezbollah's leader, Secretary General Hassan Nasrallah, gave a speech on Monday in which he said Israel's recent attack on the Iranian embassy compound in Damascus was the largest escalation in years.
In a previous speech on Friday, Mr Nasrallah had described the attack, which killed two senior commanders in Iran's Islamic Revolutionary Guard Corps, as a "turning point".
Brig Gen Mohammad Reza Zahedi and Brig Gen Mohammad Hadi Haji Rahimi were killed in the attack, along with five officers, Hossein Amanollahi, Mehdi Jalalati, Mohsen Sadaqat, Ali Agha Babaei and Ali Salehi Rouzbahani.
Brig Gen Zahedi was commander of the IRGC's Quds Force in Lebanon and Syria, while Brig Gen Haji Rahimi was a senior commander in the IRGC's foreign operations arm.
Mr Nasrallah commemorated the dead Iranian generals, and lauded Brig Gen Zahedi's involvement in efforts to expel Israeli forces from Lebanon in 2000. He also defended Iran's presence in Syria more broadly and accused Israel and others of attacking the country during the Syrian civil war.
Iranian Foreign Minister Hossein Amirabdollahian arrived in Syria on Monday as part of a regional tour that began in Oman, Iran's semi-official news agency Tasnim reported. He held talks with senior Syrian officials about issues including the situation in Gaza, it said.
He also inaugurated the country's new consulate in Damascus on Monday in the presence of his Syrian counterpart Faisal Mekdad – a symbolic reopening after consular services restarted on Sunday.
Iran has vowed to avenge the deaths of the IRGC members killed in the Damascus strike. It has warned that Israel's embassies are no longer safe.
