DEIR AL-BALAH, Gaza Strip (AP) — The Israeli military said Thursday it was looking into whether Hamas’ top leader Yahya Sinwar was killed in a military operation in Gaza. Authorities were conducting DNA tests on a body to determine if it is him, an Israeli security official said.

The military said in a statement that three militants were killed during operations in Gaza, without specifying where or elaborating further. It said the identities of the three were so far not confirmed, but it was “checking the possibility” that one of them was Sinwar.

The security official, who spoke on condition of anonymity to discuss an ongoing investigation, said the tests on the body had not yet confirmed if it was Sinwar's.

There was no immediate comment by Hamas on the report.

Sinwar was one of the chief architects of Hamas’ attack on Israel on Oct. 7, 2023, and Israel has vowed to kill him since the beginning of its retaliatory campaign in Gaza. If confirmed, Sinwar's death could be a heavy blow to the militant group. He has been Hamas' top leader inside the Gaza Strip for years, closely connected to its military wing while dramatically building up its capabilities.

Sinwar was chosen as Hamas's top leader after his predecessor, Ismail Haniyeh, was assassinated in July in an apparent Israeli strike in the Iranian capital Tehran. Israel has also claimed to have killed the head of Hamas' military wing Mohammed Deif in an airstrike, but the group has said he survived.

President Joe Biden has been briefed on Israel's investigation into whether it killed Sinwar, and U.S. officials have been in close contact with Israeli officials throughout Thursday morning, according to a senior administration official.

The report came as Israeli forces continued a more than week-old major air and ground assault in the Jabaliya refugee camp in northern Gaza. On Thursday, an Israeli strike hit a school sheltering displaced Palestinians, killing at least 15 people, including five children, according to Gaza’s Health Ministry.

Fares Abu Hamza, head of Gaza Health Ministry’s local emergency unit, said dozens of people were wounded. He said the nearby Kamal Adwan Hospital was struggling to treat the casualties.

“Many women and children are in critical condition,” he said.

The Israeli military said it targeted a command center run by Hamas and Islamic Jihad inside the school. It provided a list of around a dozen names of people it identified as militants who were present when the strike was called in. It was not immediately possible to verify the names.

Israel has repeatedly struck tent camps and schools sheltering displaced people in Gaza. The Israeli military says it carries out precise strikes on militants and tries to avoid harming civilians, but its strikes often kill women and children.

In a separate development, a building in central Beirut that houses offices of the Al Jazeera news network and the Norwegian Embassy was evacuated after a warning.

Mazen Ibrahim, Al Jazeera’s Lebanon bureau chief, said the building’s administration received three calls telling everyone to leave the building, which he said also houses the embassies of Norway and Azerbaijan, as well as dozens of offices. He said it was unclear who called in the warning.

Norwegian Foreign Ministry spokesperson Ragnhild Simenstad said the building was evacuated after a “bomb threat,” without elaborating.

Israel has ordered the evacuation of several buildings, as well as entire cities, towns and villages, as it strikes what it says are targets linked to the Hezbollah militant group.

There have also been several instances of evacuation warning calls and text messages that turned out to be bogus, which Lebanese security agencies say they are investigating.

Israel launched its campaign in Gaza to eliminate Hamas after the militants stormed into southern Israel on Oct. 7, 2023, killing some 1,200 people, mostly civilians, and abducting around 250 others. Some 100 captives are still inside Gaza, about a third of whom are believed to be dead.

Israel’s offensive has killed over 42,000 Palestinians, according to Gaza’s Health Ministry. It does not differentiate between civilians and combatants but says women and children make up a little more than half of the fatalities.

Northern Gaza was the first target of Israel’s ground invasion nearly a year ago and has suffered the heaviest destruction of the war, with entire neighborhoods in Gaza City and other towns reduced to rubble. Most of the population fled after Israel issued evacuation orders in the opening days of the war, but about 400,000 are believed to have remained despite the harsh conditions.

Earlier this month, Israel once again ordered the full-scale evacuation of the north, and allowed no food aid to enter the area for around two weeks. That led many Palestinians to fear that it had adopted a surrender-or-starve strategy suggested by former Israeli generals.

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

Since the start of the conflict, Israeli forces have launched repeated operations into Jabaliya, a densely populated urban refugee camp dating back to the 1948 war surrounding Israel’s creation. The military says militants have repeatedly regrouped there after major operations.