An Israeli airstrike in the Gaza Strip killed three sons of Hamas leader Ismail Haniyeh on Wednesday, relatives and official Hamas media said, with Haniyeh accusing Israel of acting in “the spirit of revenge and murder.”

Haniyeh’s sons are among the highest-profile figures to have been killed in the war so far. It was not immediately clear how their deaths might affect the months-long cease-fire talks being brokered by international mediators.

Haniyeh confirmed the deaths on Wednesday 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.

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

“The enemy believes that by 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 had 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 travelling 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 against 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.