Hamas deputy leader Saleh Al Arouri killed in Israeli strike in southern Beirut

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The deputy head of Hamas' political bureau and at least six others were killed in an Israeli drone strike on one of the group's offices in southern Beirut on Tuesday, the Palestinian armed faction said, in the first direct attack on the Lebanese capital since the Gaza war began in October.

A powerful explosion struck the Hamas office in the suburb of Dahieh, Lebanon’s National News Agency reported, with footage showing smoke and flames billowing from the site after a series of loud explosions.

Saleh Al Arouri, deputy head of the Hamas political bureau, was killed in the strike, Hamas confirmed.

Ismail Haniyeh, a senior political leader in Hamas, confirmed in a televised address that Mr Al Arouri and six other Hamas officials and militants had been killed in the strike.

"This crime shall make us stronger," he said. "This is a terrorist act and a violation of Lebanon's sovereignty."

A Hamas official told The National last week that Israel was unlikely to attack the group's leaders in Lebanon, as that would signal a major escalation on Hezbollah's territory.

Israel did not immediately claim responsibility. Prime Minister Benjamin Netanyahu in November said Hamas leaders would be targets “wherever they are”.

Security sources in Egypt in direct contact with Hamas said the militant group’s leader in Gaza, Yahya Sinwar, had told Egyptian mediators following news of Mr Al Arouri's death that negotiations to end the Gaza war would be indefinitely suspended.

Hamas negotiators have consistently demanded that any deal with Israel to end the war must include guarantees that Israel would not attack the group’s leaders in Gaza or elsewhere.

The strike marks a major escalation in Israel's attacks on Lebanon, which until now have concentrated on southern border areas. It coincides with the anniversary of the US assassination of the late Maj Gen Qassem Suleimani, a senior commander in the Iranian Revolutionary Guards Corps Quds Force, in Iraq.

An official from the Lebanese Hezbollah group, a close ally of Hamas, said two members of Hamas's armed wing, the Ezzedine Al Qassam Brigades, were also killed.

“The occupation [Israel] will pay the price,” the official added.

In a televised address last year, Hezbollah leader Hassan Nasrallah warned Israel against conducting targeted assassinations in Lebanon.

“Any assassination on Lebanese lands that targets a Lebanese or a Syrian or an Iranian or a Palestinian will face a strong response,” he said in August. “It will not be tolerated. We will not allow Lebanon to become a new field of assassinations for Israel.”

Videos circulating on Telegram channels and social media showed the extent of the destruction after the assassination, with an entire floor blown out of a multistorey building and several cars destroyed.

Tuesday's strike occurred in the heavily populated residential neighbourhood of Msharafieh, in the southern Beirut suburb of Dahieh.

“I almost died,” said Abou Adel, owner of a restaurant in front of the targeted building.

He said that part of the missile had hit the counter where he and his colleague, Mohamed Mahdi, were standing.

“We heard three strikes and immediately thought it was Israel,” he added. “Tomorrow, Hassan Nasrallah will speak, and it's up to him to decide. We trust his decisions.

“But there should be a strong response. God willing, we will hit Tel Aviv, and we're not afraid of the war spreading because this is a significant escalation in the heart of Dahieh."

Leader-in-exile Mr Al Arouri was a founding member of Al Qassam Brigades and deputy chairman of Hamas’s political bureau.

He was exiled from Gaza in 2014 and relocated to Turkey before moving to Lebanon. Hamas’s media department released a video of Mr Al Arouri shortly after the announcement of his death, calling it “the last message from the martyr Sheikh Saleh Al Arouri to the Palestinian people”.

In the video, Mr Al Arouri called on Palestinian youth to “resist with rocks, with guns, with handmade rifles, with everything and anything you have on hand to resist”.

“This is our land,” he said, referring to Palestine.

More than 150 people, including at least 19 civilians, have been killed in Israeli strikes on Lebanon since border clashes began on October 8.

Israel has launched attacks on Hamas and Hezbollah, which have both launched missiles into northern Israel, leaving southern Lebanese villages fearing an expansion of the conflict.

Iran Tuesday evening warned that the killing of Mr Al Arouri would further ignite resistance against Israel, "not only in Palestine but also in the region," according to Iranian Foreign Ministry spokesman Nasser Kanaani.

Brian Katulis, a senior fellow and vice president of policy at the Middle East Institute, said the strike could signal things to come as Israel shifts some of its forces away from Gaza.

“This may be the first of many [strikes] as the Israelis ramp down parts of their combat operations in Gaza,” Mr Katulis told The National.

“They'll look for ways to continue to degrade what they see as the threat posed by Hamas regionally. It may be sort of a turning point in terms of how Israel may be moving away from high intensity combat operations in Gaza.

"I think it launches us into an even more uncertain and dangerous phase.”

The US Department of Sate said that Mr Al Arouri had worked closely with the late Islamic Revolutionary Guards Corps (IRGC) commander Qassem Suleimani, who was killed in a US drone strike near Baghdad airport on January 3, 2020

The killing of the Hamas leader came hours before the anniversary of Mr Suleimani's assassination.

Jihan Abdalla in Washington and Hamza Hendawi in Cairo contributed to this report