The Israeli military announced on Saturday night that it had killed Muhammad Sinwar, one of Hamas’s top military commanders in Gaza, during airstrikes this month that targeted the vicinity of a hospital in southern Gaza.

Hamas did not immediately respond to the claim of Mr. Sinwar’s death. During the war in Gaza, the Palestinian armed group has largely not confirmed the killing of its commanders in the moment, only announcing their demise weeks or even months later, if at all.

Mr. Sinwar’s death would be a blow to Hamas. The brother of Yahya Sinwar, the former Hamas leader killed by Israel last year, he was one of the most powerful Hamas leaders in Gaza still alive after nearly 20 months of war with Israel.

But Mr. Sinwar’s death may not immediately change Hamas’s strategy or operations, analysts said. Since the war began more than a year and a half ago, Israel has targeted and killed a number of Hamas’s top leaders, only to see the group continue its insurgency war against Israel in Gaza.

This month, Israeli aircraft struck an underground compound near the European Hospital, close to the southern Gaza city of Khan Younis, where Mr. Sinwar had recently been present, according to the Israeli military. At the time, Israeli officials said privately that they had been targeting Mr. Sinwar, but they did not mention him in their announcement of the strikes.