An Israeli airstrike on Wednesday killed three sons of one of the most senior leaders of Hamas, Ismail Haniyeh, who said the strike would not weaken the group’s negotiating position or its resolve in its fight against Israel.

Mr. Haniyeh, who leads the Hamas political bureau from exile, is a longstanding leader of the group. He is also engaged in the stalled negotiations with Israel through international mediators who are seeking to broker a cease-fire and secure the release of Israeli hostages held by Hamas in the Gaza Strip.

“The enemy is delusional if it thinks that by killing my children, we will change our positions,” Mr. Haniyeh said in a statement. “We shall not give in, no matter the sacrifices.”

Israeli ground troops have largely pulled out of Gaza, but Israel continues to conduct airstrikes across the territory as well as wage battles in a corridor in central Gaza where the Israeli military has maintained a presence.

Mr. Haniyeh, who has long shuttled between Qatar and Turkey, said in the statement that 60 members of his extended family had been killed by Israel over time and that the strike on Wednesday had killed some grandchildren in addition to the three sons.