Tel Aviv, Israel. Three sons and three grandchildren of Hamas' top political leader were killed Wednesday by an Israeli airstrike in the Gaza Strip, and the leader accused Israel of acting in “the spirit of revenge and murder.”

Ismail Haniyeh's sons are among the highest-profile figures to be killed in the war so far. It was not immediately clear how their deaths might affect the monthslong cease-fire talks being brokered by international mediators, though Haniyeh said Hamas would not cave into the pressure.

The Israeli military said the men conducted militant activity in central Gaza, without elaborating.

Haniyeh confirmed the deaths in an interview with the Al Jazeera satellite channel, saying his sons “were martyred on the road to liberating Jerusalem and the Al-Aqsa Mosque.”

“The criminal enemy is driven by the spirit of revenge and murder and does not value any standards or laws,” he said in the phone interview.

The Israeli military described the three siblings as a cell commander and two military operatives.

In his interview with Al Jazeera, Haniyeh said the killings would not pressure Hamas into softening its positions.

“The enemy believes that targeting the families of the leaders, it will push them to give up the demands of our people,” he said. “Anyone who believes that targeting my sons will push Hamas to change its position is delusional.”

Haniyeh lives in exile in Qatar, where Al Jazeera is based. Hamas' Al-Aqsa TV station aired footage of Haniyeh receiving the news of the deaths while visiting wounded Palestinians who have been transported to a hospital in Doha. As an aide received the news on his phone, Haniyeh nodded, looked down at the ground and slowly walked out of the room.

“There is no might and no power but by God,” Haniyeh muttered. “May God make matters easy for them.”

Al-Aqsa TV said Hazem, Ameer and Mohammed Haniyeh were killed with family members in the strike near the Shati refugee camp in Gaza City. Ismail Haniyeh is originally from Shati.

The brothers were traveling with family members in a single vehicle targeted by an Israeli drone, Al-Aqsa TV said, adding that a total of six people were killed, including a daughter of Hazem Haniyeh and a son and daughter of Ameer.

Earlier, Israeli war cabinet minister Benny Gantz claimed Hamas has been defeated militarily, although he also said Israel will fight it for years to come.

“From a military point of view, Hamas is defeated. Its fighters are eliminated or in hiding” and its capabilities “crippled,” Gantz said in a statement to the media in Sderot.

But he added: “Fighting against Hamas will take time. Boys who are now in middle school will still fight in the Gaza Strip.”

Gantz reiterated the Israeli government's commitment to go into Rafah, the city at the far southern tip of the Gaza Strip where more than half the territory's 2.3 million people are now sheltering. "Wherever there are terrorist targets -- the IDF will be there,” he said, referring to the Israeli military.

The strike came as Palestinians in Gaza marked a muted Eid al-Fitr holiday, which ends the holy fasting month of Ramadan, by visiting the graves of loved ones killed in the war. In the Jabaliya refugee camp near Gaza City, people sat quietly by graves surrounded by buildings destroyed by Israel's offensive in response to the deadly Hamas attack on Oct. 7.