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Hamas has named Yahya Sinwar as its new political leader following the assassination of its chief Ismail Haniyeh in Tehran last week.
The news was confirmed in a statement published by the group on Telegram.
“The Islamic Resistance Movement Hamas announces the selection of leader Yahya Sinwar as head of the movement's political bureau, succeeding the martyr leader Ismail Haniyeh, may God have mercy on him,” it read.
Mr Sinwar, one of the founding members of Hamas, is the head of its operations in Gaza and has overseen the group's activities in the war-torn enclave since 2017.
He is considered the mastermind of the October 7 attack on southern Israel which sparked the current war, and is one of Israel's most-wanted targets.
He has not made any public appearances since the war began, although the Israeli army has published footage it claims to show the leader in a Gaza tunnel on October 10.
“Yahya Sinwar is the commander … and he is a dead man,” Israel's army spokesman Rear Admiral Daniel Hagari said in early October.
In December, the Israeli army issued a $400,000 bounty on Mr Sinwar and dropped leaflets over Gaza offering cash rewards for information leading to his capture.
The announcement comes less than a week after the suspected Israeli assassination of Mr Haniyeh, who was killed while staying at an Islamic Revolutionary Guard Corps (IRGC) guesthouse in Tehran after attending the inauguration of Iranian President Masoud Pezeshkian.
Hamas, Iran and regional allies have vowed “harsh punishment” against Israel over the attack, sending tensions soaring and raising the prospect of an all-out war with Lebanon, where the Iran-backed Hezbollah militant group is based.
Mr Haniyeh was a chief negotiator for the militant group in delicate months-long efforts to broker a ceasefire in Gaza, where almost 40,000 Palestinians have been killed and more than 90,000 wounded since the war began.
Hamas said the negotiations, brokered by Qatar and Egypt, were "clinically dead" following the suspected assassination, which has not been publicly claimed by Israel, and would not resume for at least a week.
It is unclear how the new appointment will affect ceasefire talks.
However, Hamas political bureau member Osama Hamdan said that the negotiations to stop the war in Gaza shall continue “under the supervision” of the group’s new leader.
He added in a statement that "the negotiations were conducted by the leadership, and Mr Sinwar was always present and he was not far from the negotiations”.
“It is too early to talk about what the negotiation process will lead to,” he stressed; however, the team “that followed the negotiations under the leadership of the martyr (Ismail) Haniyeh will continue to do so under the supervision of Mr Sinwar”.
Mr Hamdan said that the new chief was “unanimously” chosen to lead the group. “Mr Sinwar is accepted by everyone in the group and is the subject of consensus."
The news also comes as the war threatens to spill over into an all-out conflict in Lebanon, where Israeli jets broke the sonic barrier several times on Tuesday evening as Hezbollah leader Hassan Nasrallah spoke for the first time since the death of Mr Haniyeh and Hezbollah commander Fouad Shukr, killed just hours apart.
He said Israel's punishment "is coming" and claimed other regional allies would also stage attacks on Israel, which has been on high alert since last week.
Iran has threatened a direct attack in the near future, citing its "duty" to avenge Mr Haniyeh.
Israeli authorities have upped GPS jamming in Tel Aviv and central parts of the country, while local councils in the south have opened public bomb shelters and northern residents have been told to avoid any non-essential travel.
At least 19 people were wounded in an explosion in the northern city of Nahariya earlier on Tuesday, later said to be caused by an army interceptor missing its target.
Many nations have also urged their citizens to immediately leave Lebanon for fear the war will imminently escalate.