The Israeli military targeted the de facto leader of Hamas in Gaza with an airstrike, the Israeli authorities announced on Friday, in what would be the most senior Hamas official Israel has tried to kill since a cease-fire began last fall.

The Hamas commander targeted by Israel, Izz al-Din al-Haddad, took over the group’s military wing in Gaza last year, after Israeli forces killed Muhammad Sinwar, the brother of Yahya Sinwar, an architect of Hamas’s deadly attack on Israel on Oct. 7, 2023.

In a joint statement on Friday, Israel’s prime minister and defense minister described Mr. al-Haddad as another architect of that attack, and said that he had “refused to implement the agreement” brokered by President Trump “to disarm Hamas and demilitarize the Gaza Strip.”

Hamas did not immediately respond to the claim that Mr. al-Haddad had been targeted in an attack.

Mr. al-Haddad was the target of the airstrike on a building in Gaza, and the Israeli Air Force also struck around the structure in order to prevent an escape, according to two Israeli defense officials who spoke on condition of anonymity to discuss operations in Gaza. Israeli analysts think it was likely that Mr. al-Haddad was killed inside the building, the officials said.

Accounts of how many were killed and wounded in the attack differed as of Friday evening.

Dr. Mohammed Abu Salmiya, the director of al-Shifa hospital in Gaza, said in a text message that at least seven people were killed in the strikes on Gaza City, and 10 others were wounded. Mahmoud Basl, a spokesman for Gaza’s Civil Defense emergency service, said by phone that five people had been killed in the strikes.

Experts, as well as a senior official of Mr. Trump’s Board of Peace, say that Israel has repeatedly violated the October 2025 cease-fire with almost daily airstrikes in Gaza. Experts also say Israel has violated the agreement by taking control of territory beyond the truce lines and by hampering the delivery of humanitarian aid and rubble-removal equipment.

Israeli officials have accused Hamas leaders, including Mr. al-Haddad, of violating the cease-fire by trying to restore their military abilities, planning new attacks and refusing to disarm.

Mr. al-Haddad, in his mid-50s, was believed to be firmly opposed to Israeli efforts to dislodge Hamas from power in Gaza, and was thought to be based in Gaza City. Since the Oct. 7 attack, he has been the only senior Hamas commander to give an on-the-record interview, appearing in an Al Jazeera documentary that aired last year.

Known to his Hamas compatriots as Abu Suheib, he was one of the few remaining living commanders who was a member of the militant group’s high-level military council on Oct. 7. A Hebrew speaker, Mr. al-Haddad also spent time with Israeli hostages in northern Gaza, according to Israeli officials. He rose into higher leadership positions as Israel killed one senior Hamas leader after another, including Muhammad Deif, the leader of the military wing, his deputy Marwan Issa, and the Sinwar brothers.

Records from the Gaza health ministry indicate that Mr. al-Haddad’s eldest son, Suheib, was among the people killed during the war, which has left tens of thousands of Gazans dead. In April, the Shin Bet, the Israeli domestic intelligence agency, announced the killing of Mahmoud Abu Hiseira, whom it described as Mr. al-Haddad’s right-hand man.

So far, Hamas has resisted demands that it relinquish its military wing’s weapons. A top official of the Board of Peace, Nickolay Mladenov, accused Hamas this week of blocking efforts to help Palestinians, and urged it to surrender its weapons and make room for the National Committee for the Administration of Gaza, a U.S.-appointed group of Palestinian technocrats waiting to enter Gaza and assume control over government functions.

A Hamas spokesman, Hazem Qassim, said this week that the Hamas-run government in Gaza was ready to hand over the administration of the territory to the National Committee, without saying whether the group’s military wing was willing to give up its weapons.

Ronen Bergman contributed reporting.