Hamas says it has chosen Yahya Sinwar, its top official in Gaza, as the new leader of its political bureau.

The selection of Sinwar follows Ismail Haniyeh’s assassination in Tehran on July 31, the Palestinian group said on Tuesday.

“The Islamic Resistance Movement Hamas announces the selection of Commander Yahya Sinwar as the head of the political bureau of the movement, succeeding the martyr Commander Ismail Haniyeh, may [God] have mercy on him,” the group said in a brief statement.

Sinwar, 61, is seen by Israel as the mastermind behind the October 7 attack by Hamas inside Israeli territory, in which more than 1,100 people were killed and more than 200 others taken captive.

Israel’s subsequent military campaign in Gaza has killed nearly 40,000 Palestinians, thousands of them women and children, displaced almost its entire 2.3 million population, and caused an unprecedented humanitarian crisis with widespread starvation and health emergencies.

The Israeli assault has also come with reports of systematic rights abuses, such as the torture of Palestinians in captivity.

Haniyeh’s assassination, almost certainly carried out by Israel, sent shockwaves through the region and was seen by many as an effort by the government of Israeli Prime Minister Benjamin Netanyahu to scuttle efforts to negotiate a ceasefire, in which Haniyeh was a key figure.

Analysts have said his replacement by Sinwar, who has gone largely unseen since the October 7 attack was an indicator of the central place that Gaza occupies in the group’s political vision.

“He [Sinwar] has skyrocketed to an influential position in Hamas, leading it in Gaza. The choice of Hamas to name him leader of the movement now puts Gaza front and centre of, not just the events on the ground, but certainly of the dynamics in the Hamas movement,” Nour Odeh, a Palestinian political analyst based in Ramallah, told Al Jazeera.

“And it really sends a signal, as far as negotiations of a ceasefire is concerned, that Gaza calls the shots.”

Sinwar was born in a Gaza refugee camp, south of Khan Younis, and was the former head of the Al-Majd security apparatus, tasked with eliminating Palestinians suspected of collaborating with Israel. He became the leader of Hamas in the Gaza Strip in 2017.

Sinwar is one of several Hamas leaders for whom the International Criminal Court (ICC) sought an arrest warrant over allegations of war crimes committed on October 7.

Warrants were also sought for some Israeli leaders, including Netanyahu and Israeli defence chief Yoav Gallant, for alleged war crimes in Gaza.

But despite Israel’s promise to wipe out Hamas, and a military campaign that ranks among the most destructive in modern history, the Palestinian armed group has continued to hold out against Israeli forces in Gaza.

Sinwar has likewise managed to evade capture by Israel, despite a proclamation by Gallant that Sinwar was living “on borrowed time” after October 7.

“I think the focus on Gaza, and the focus on Sinwar, is a major signal of defiance,” Al Jazeera senior political analyst Marwan Bishara said.

“And of the fact that Hamas is not about to lose Gaza, that Hamas is going to remain a power within Gaza, and hence its leader is there."