Israel says it is examining the possibility that Hamas leader Yahya Sinwar, a mastermind of the October 7, 2023 attack that sparked the war in Gaza, was killed in a military operation. Authorities were conducting DNA tests on a body to determine whether it was him, an Israeli security official said.

The military said in a statement that three militants were killed in operations in Gaza, without specifying the location or elaborating.

There was no immediate comment from Hamas on the report.

Sinwar's death would be a significant moment in Israel's years-long offensive against the militant group and could complicate efforts to release dozens of hostages held in Gaza.

Sinwar became head of Hamas after former leader Ismail Haniyeh was killed in an explosion in Iran in July that was widely blamed on Israel.

Some things you should know about Sinwar:

From refugee camp to Hamas fighter

Sinwar was born in 1962 in a refugee camp in the city of Khan Younis in the Gaza Strip. He was an early member of Hamas, which was founded in 1987. He eventually led the group's security arm, which worked to rid it of informants for Israel.

Israel arrested him in the late 1980s and he admitted killing 12 suspected collaborators, a role that earned him the nickname “The Butcher of Khan Younis.” He was sentenced to four life sentences for crimes including the killing of two Israeli soldiers.

A prison warden

Sinwar organized prison strikes to improve working conditions. He also studied Hebrew and Israeli society.

He survived a brain tumor in 2008 after being treated by Israeli doctors.

Sinwar was among more than 1,000 Palestinian prisoners released by Prime Minister Benjamin Netanyahu in 2011 as part of an exchange for an Israeli soldier captured by Hamas in a cross-border raid.

Rise to power in Gaza

When Sinwar returned to Gaza, he quickly rose through Hamas' leadership ranks and was known for his ruthlessness. He is widely believed to be behind the 2016 assassination of another top Hamas commander, Mahmoud Ishtewi, in an internal power struggle.

Sinwar became head of Hamas in Gaza, effectively gaining control of the area, and worked with Haniyeh to align the group with Iran and its proxies in the region while expanding the group's military capabilities.

The October attack on Israel

Sinwar is believed to have planned the surprise attack on Israel on October 7 along with Mohammed Deif, the head of Hamas' armed wing.

The attack killed about 1,200 people, mostly civilians, and sparked a war that has killed over 42,000 Palestinians in Gaza, according to health authorities there.

Hamas said it launched the attack in retaliation for Israel's treatment of Palestinians and to put the Palestinian cause back on the world agenda.

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

Israel said it killed Deif in an attack in July, while Hamas says he is still alive.

Where would this lead Hamas?

Sinwar has been in hiding since the attack and ceasefire negotiators have said it could take several days to send and receive messages from him.

Even before Sinwar became Hamas' top leader, he was believed to have the final say on any agreement to release hostages held by the militant group. About 100 hostages remain in the Gaza Strip, about a third of whom are believed to be dead.

It is unclear who would replace Sinwar and what that might mean for the ceasefire effort, which stalled in August after months of negotiations between the United States, Egypt and Qatar.

Hamas has hundreds of thousands of followers in the Gaza Strip, the Israeli-occupied West Bank and in Palestinian refugee camps across the region. Several of its top politicians are based in Qatar, which has acted as an intermediary between Israel and the militant group.

Israel has arrested and killed several senior Hamas leaders and militant commanders over the years, and the militant group has quickly replaced them. But it has never fought a prolonged war against Israel and claims to have killed dozens of senior militants and over 17,000 fighters, although it has provided no evidence for the latter figure.

More updates on the Israel-Hamas war

Israeli forces continued a major air and ground attack on the Jabaliya refugee camp in the northern Gaza Strip that lasted more than a week. On Thursday, an Israeli attack hit a school housing displaced Palestinians, killing at least 28 people, according to Gaza's health ministry.

Fares Abu Hamza, head of the Gaza Health Ministry's emergency unit in the north, said a woman and four children were among the dead, correcting an earlier report of five children. He said dozens of people were injured.

The Israeli military said it attacked a Hamas and Islamic Jihad command center at the school. She provided a list of around a dozen names of people she identified as militants who were present at the time of the attack call. It was not immediately possible to verify the names.

Israel has repeatedly attacked tent camps and schools housing displaced people in Gaza. The Israeli military says it carries out targeted attacks on militants and tries not to harm civilians, but its attacks often kill women and children.

According to Gaza's Health Ministry, the Israeli offensive has killed over 42,000 Palestinians. No distinction is made between civilians and combatants, but it is said that women and children make up just over half of the deaths.

The northern Gaza Strip was the first target of Israel's ground invasion nearly a year ago and has suffered the worst destruction of the war, with entire neighborhoods in Gaza City and other cities reduced to rubble. Most of the population fled after Israel issued evacuation orders in the early days of the war, but around 400,000 are believed to have remained despite the harsh conditions.

Earlier this month, Israel again ordered a complete evacuation of the north and stopped food aid from entering the area for about two weeks. This led many Palestinians to fear that it was a surrender-or-starve strategy proposed by former Israeli generals.

Israel allowed two aid shipments to the north earlier this week after the United States warned it could reduce its military aid if its ally did not do more to address the humanitarian crisis.