Hamas terror chief Yahya Sinwar has been killed during an Israeli military operation in the Gaza Strip, the Israel Defense Forces announced Thursday.

The IDF and Israel's Shin Bet intelligence agency released a joint statement saying it can "confirm that after a year-long pursuit, yesterday (Wednesday), October 16, 2024, IDF soldiers from the Southern Command eliminated Yahya Sinwar, the leader of the Hamas terrorist organization, in an operation in the southern Gaza Strip. 

"Yahya Sinwar planned and executed the October 7th Massacre, promoted his murderous ideology both before and during the war, and was responsible for the murder and abduction of many Israelis," the statement added. "Yahya Sinwar was eliminated after hiding for the past year behind the civilian population of Gaza, both above and below ground in Hamas tunnels in the Gaza Strip."

Referred to by Israel as the Butcher of Khan Younis for his violent and cruel torture methods against his enemies, both Israeli and Palestinian, Sinwar, 61, is widely seen as being behind the massacre of Israeli civilians carried out by thousands of Hamas militants on Oct. 7. 

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Yahya Sinwar chairs a meeting with leaders of Palestinian factions at his office in Gaza City, April 13, 2022.  (AP)

The IDF and Shin Bet said earlier Thursday that "During IDF operations in the Gaza Strip, three terrorists were eliminated" and that it was "checking the possibility that one of the terrorists was Yahya Sinwar." 

An Israel Army Radio report said Thursday that Sinwar was killed during a battle with Israeli soldiers. 

The soldiers had spotted suspected terrorists in Gaza and opened fire before the individuals fled into a building, according to the report. It added that a tank then fired a shell at the building, causing it to collapse.

When the soldiers went inside to examine the aftermath, they found three bodies – one of which ultimately has been identified as Sinwar.

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"The master murderer, Yahya Sinwar, who is responsible for the massacre and atrocities of October 7, was killed today by IDF soldiers," Foreign Minister Israel Katz also told Fox News in a statement.

A U.S. defense official has told Fox News that Secretary of Defense Lloyd Austin was passed a note during a NATO Defense Ministerial meeting on Sinwar’s death. The Israelis, the official says, notified U.S. Department of Defense officials and have passed along photos.

Israeli Defense Minister Yoav Gallant, left, Shin Bet leader Ronen Bar, center, and General Staff Lt. Gen. Herzi Halevi of the Israel Defense Forces, right, are seen speaking Thursday near the Gaza border. Israel confirmed Thursday it has killed Hamas leader Yahya Sinwar. (IDF)

The Hostages and Missing Families Forum said in a statement Thursday that it "commends the security forces for eliminating Sinwar, who masterminded the greatest massacre our country has ever faced, responsible for the murder of thousands and the abduction of hundreds.

"However, we express deep concern for the fate of the 101 men, women, elderly and children still held captive by Hamas in Gaza. We call on the Israeli government, world leaders, and mediating countries to leverage the military achievement into a diplomatic one by pursuing an immediate agreement for the release of all 101 hostages: the living for rehabilitation and the murdered for proper burial," it added.

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In Washington, House Speaker Mike Johnson said ""Justice has once again been served by the brave men and women of the Israeli military."

"At this moment, with the bloodthirsty leaders of Hamas and Hezbollah now gone, the Biden-Harris Administration must now work in tandem with Israel to apply a maximum pressure campaign against the head of the snake: Iran," Johnson added.

Sen. Lindsey Graham, R-S.C., also said ""The Israeli people – through their political leadership, the IDF and their intelligence services – have delivered a mighty blow to Hamas and Iran, and rendered some sense of justice with the elimination of Sinwar."

General Staff Lt. Gen. Herzi Halevi of the Israel Defense Forces, right, and Ronen Bar, the leader of Shin Bet, conduct a situational assessment on Thursday, Oct. 17. (IDF)

Israeli Defense Forces spokesman Lt. Col. Richard Hecht had told reporters last October that "Sinwar is the leader of Hamas in Gaza and he’s a dead man walking." 

"We will get to him, however long it takes… and this war could be long," he said. 

Sinwar was believed to be somewhere in the Palestinian enclave but hidden deep underground in the warren of tunnels Hamas uses to transport weapons and fighters and where they may even be keeping the hostages, was born in the Khan Younis refugee camp when the area was part of Egypt. 

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According to multiple sources, he was always a militant activist and joined Hamas not long after its founding in 1987. Two years later, he was arrested by Israel for his involvement in the abduction and killing of two Israelis, as well as the torturing and murder of four Palestinians he considered to be collaborators.  

Yahya Sinwar appears during a ceremony for Hamas fighters killed by Israeli airstrikes at Yarmouk football stadium in May 2021 in Gaza City. (Laurent Van der Stockt/Getty Images)

Sentenced to life in prison, Sinwar ended up serving 22 years in an Israeli jail and was eventually released as part of a prisoner exchange for the abducted Israeli soldier Gilad Shalit in 2011. 

"Sinwar has been active since the early days of Hamas," Kobi Michael, a senior researcher at the Institute for National Security Studies in Tel Aviv, previously told Fox News Digital. "In jail, he became a prominent leader of Hamas prisoners and was a very influential figure among all Palestinian prisoners."  

After being returned to Gaza as part of the Shalit deal, Sinwar became a popular leader in Hamas, an affiliate of the Muslim Brotherhood, and in 2017 was elected by secret ballot to replace the incumbent political leader, Ismail Haniyeh, who was killed in Iran this July. 

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Following Haniyeh’s death, Sinwar was named Hamas’ new leader.  

Fox News' Trey Yingst, Yonat Friling and Liz Friden contributed to this report.