Saleh Al-Aruri, 57, was killed in a "treacherous Zionist strike," Hamas said on its official channel.
A high-level security official in Beirut told AFP that Aruri was killed in the Israeli strike along with his bodyguards in the Lebanese capital's southern suburbs, which is a stronghold of Hamas ally Hezbollah.
At least 4 people were killed in a Beirut explosion targeting the Hamas office after a drone attack in the Mashrafiyah area, said NNA, Lebanon’s state news agency
Hamas confirmed that two of its leading figures - Samir Fandi Abu Amer and Azzam Al-Aqrae Abu Amar - were killed in the attack
Saleh Al-Aruri
Saleh Al-Aruri, born in Ramallah in 1966, was a senior leader of Hamas and a founding commander of its military wing, the Ezz Eddin Al-Qassam Brigades.
He was a deputy chairman of Hamas's political bureau.
Al-Aruri served as Hamas's military commander of the West Bank.
He was based in Lebanon at the time of his assassination.
Hamas responds
Hamas vowed Tuesday that the killing of the group's deputy in Lebanon will not "undermine the continued brave resistance" in Gaza where the Palestinian group is battling Israeli forces.
"It proves once more the utter failure of the enemy to achieve any of its aggressive goals in the Gaza Strip," senior Hamas official Izzat Al-Rishq said in a statement.
Shortly after the attack on Aruri, "Prime Minister Najib Mikati condemned the explosion in the southern suburbs of Beirut that killed and injured many," his office said in a statement.
The attack "aims to draw Lebanon into a new phase of confrontations" with Israel, added the statement.
It comes at a time when Hamas ally Hezbollah has been exchanging daily cross-border fire with Israeli forces in southern Lebanon.
Hassan Nasrallah, the leader of Hezbollah, has previously vowed that the Lebanese resistance will respond to any Israeli assassination on Lebanon's soil.
More condemnations
Fattah issued a statement decrying the assassination of Saleh Al-Aruri saying "it reflects the criminal mindset of the occupation toward the Palestinian people and their leaders."
The Iranian foreign ministry issued a statement saying: "We strongly condemn the assassination of Al-Aruri. The Zionist entity is held responsible for the repercussions of its new misadventure."
An adviser to Prime Minister Benjamin Netanyahu said "We have not claimed responsibility for the attack in Beirut but the attack did not target Lebanon or Hezbollah."
In a statement, Islamic Jihad said the assassination of Al-Aruri "is an attempt by the enemy to broaden the scope of confrontations to drag the region into war as a way of escaping from the fact of its failure in Gaza.
Track record
Shortly after the start of its war on Gaza, Israel "vowed" to assassinate Hamas leaders in exile around the world.
Israel has a track record of assassinating leading Palestinian figures from various shades of the Palestinian national movement.
In March 2004, Israel assassinated Sheikh Ahmed Yassin, one of the founders of Hamas.
Israeli helicopters launched multiple missiles with the specific aim of targeting Sheikh Yassin as he was coming back from morning prayers at the mosque near his residence in the Sabra neighbourhood of Gaza.
Over the decades, Israel assassinated many key figures in the Palestine Liberation Organization (PLO) and other Palestinian factions.
These assassinated figures included Ghassan Kanafani, a well-known novelist and spokesperson for the leftist Popular Front for the Liberation of Palestine (PFLP), in Beirut in 1972.
They also included Fatah leaders Khalil Al-Wazir (aka Abu Jihad) in Tunisia in 1988 and Salah Khalaf (aka Abu Eyad) in Tunisia in 1991
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