An Israeli airstrike on Gaza killed three sons of Hamas leader Ismail Haniyeh, the militant group said, among its most high-profile casualties since the start of the war six months ago.

The attack, which coincided with the Muslim holiday of Eid al-Fitr, targeted a car in the Shati refugee camp near Gaza City, Hamas said in a statement Wednesday, citing Haniyeh.

The strike comes after Israeli officials said earlier this week progress had been made in negotiations for a cease-fire in the conflict, which would include the release of Israeli hostages held by Hamas and Palestinians detained in Israeli prisons.

Hamas, designated a terrorist organization by the U.S. and European Union, said on Monday there’d been no progress in the talks.

The Israel-Hamas war began on Oct. 7, when the Iran-backed group invaded Israel and killed almost 1,200 people. That triggered a major military offensive that’s killed more than 33,000 Palestinians.

Haniyeh, who is based in Qatar, said three of his grandchildren were also killed in the strike, according to Hamas.