Israel said Hamas leader Yahya Sinwar, a key figure behind the October 7, 2023 attack on Israel, was killed in a military operation on October 17.

His death marks a significant moment in Israel's year-long offensive against Hamas. It potentially complicates hostage release efforts and the second killing of a top Hamas official in less than a year. 

Sinwar, 62, became Hamas' top leader in Gaza after the killing of his predecessor, Ismail Haniyeh, in an explosion in Iran in July widely attributed to Israel.

Born in 1962 in a Gaza refugee camp, Sinwar was an early Hamas member. He was arrested by Israel in the late 1980s and served over 20 years in prison for killing suspected collaborators and Israeli soldiers. Released in 2011 as part of a prisoner exchange, he quickly rose through Hamas' ranks.

Sinwar is believed to have engineered the October 7, 2023 attack on Israel alongside Mohammed Deif, head of Hamas' armed wing.

The International Criminal Court sought arrest warrants for Sinwar, Deif, and Haniyeh in May 2024 for their alleged roles in the attack.

The October 2023 attack killed about 1,200 Israelis and sparked a war that has resulted in over 42,000 Palestinian deaths in Gaza, according to local health authorities. Sinwar has been in hiding since the attack.

If confirmed, Sinwar's death could impact ongoing ceasefire negotiations and efforts to release the approximately 100 hostages still held in Gaza, about a third of whom are believed to be dead.

It remains unclear who will replace Sinwar as Hamas' leader in Gaza. The militant group has historically quickly replaced killed or arrested leaders, though it has never before faced such a prolonged conflict with Israel.

Israel claims to have killed dozens of high-ranking Hamas militants and over 17,000 fighters during the year-long war, though it has not provided evidence for the latter figure.

Following Iran's threat to escalate previously further, Israeli Prime Minister Benjamin Netanyahu said the Jewish state is at a high level of preparedness for any scenario, both defensively and offensively, after he completed a situation assessment with Israel's Home Front Command, his office said.