An Israeli attack in northern Gaza has killed three sons of Hamas chief Ismail Haniyeh as Israel continues its bombardment of the besieged enclave on the Muslim holiday of Eid al-Fitr.

In an interview with Al Jazeera Arabic, Haniyeh confirmed the killing of his children Hazem, Amir and Mohammad along with a number of his grandchildren on Wednesday. Shehab news agency reported that at least three grandchildren of the Hamas leader were killed in the attack.

Haniyeh said they were targeted as they were visiting relatives for Eid at Shati refugee camp.

“Through the blood of the martyrs and the pain of the injured, we create hope, we create the future, we create independence and freedom for our people and our nation,” he said, adding that around 60 members of his family, including nieces and nephews, have been killed since the start of the war.

The Hamas political leader, who is based in the Gulf state of Qatar, decried what he described as Israel’s brutality in Gaza and stressed that Palestinian leaders will not back down if their families and homes are targeted.

“There is no doubt that this criminal enemy is driven by the spirit of revenge and the spirit of murder and bloodshed, and it does not observe any standards or laws,” Haniyeh said.

“We’ve seen it violate everything on the land of Gaza. There is a war of ethnic cleansing and genocide. There is mass displacement.”

The Israeli military later said that it targeted the three sons, describing them as Hamas military operatives who were on their way to “carry out terrorist activities in the central area of the Gaza Strip”. The Israeli statement did not mention the grandchildren who were killed in the attack.

The war, which began on October 7 after Hamas launched an attack on southern Israel, has killed more than 33,400 Palestinians. The Israeli military has also levelled large parts of Gaza and imposed a strict blockade on the territory, bringing its more than two million inhabitants to the verge of famine.

Israel had said earlier this month that it withdrew its troops from southern Gaza to “prepare for future operations”, but Israeli attacks on Palestinians throughout the enclave have persisted.

For its part, Hamas aired footage on Tuesday of what it said was an ambush that killed at least 10 Israeli soldiers in the southern Gaza city of Khan Younis. Israel has announced the killing of four of its troops in Gaza this week.

On Wednesday, Haniyeh said the attack on his family is evidence of Israel’s “failure” as it continues to face Palestinian fighters in Gaza, adding that the killings will not change Hamas’s position in ongoing indirect ceasefire talks.

He stressed that Hamas would not withdraw its demands, which include a permanent ceasefire and a return of displaced Palestinians to their homes.

“If they think that targeting my children at the peak of these talks before the movement’s [Hamas’s] response is submitted will cause Hamas to change its positions, they are delusional,” Haniyeh said, referring to Israel.

“The blood of my children is not more valuable than the blood of the children of the Palestinian people … All the martyrs of Palestine are my children.”

The United States has been calling on Hamas to accept a temporary ceasefire that would see a surge in humanitarian aid to Gaza, the release of Israeli captives in the territory as well as freeing an unspecified number of Palestinian prisoners held by Israel.

On Wednesday, US President Joe Biden reiterated his support for a truce deal. “It is now up to Hamas; they need to move on the proposal that’s been made,” he told reporters. “And as I said, we get these hostages home where they belong, but also bring back a six-week ceasefire that we need now.”

The US government has called on Israel to increase the aid flow to Gaza and minimise civilian casualties, but Biden stressed his “ironclad” support to Israel against a possible Iranian attack on the country.

Iran has promised to respond to an Israeli air raid that killed seven members of its Islamic Revolutionary Guard Corps (IRGC), including two generals, at its consulate in Damascus, Syria.

Later on Wednesday, Hamas echoed Haniyeh’s message, saying that the intensifying Israeli “terrorism” and massacres in Gaza will not improve Israel’s negotiating position.

The group said Haniyeh received calls expressing condolences from Turkish President Recep Tayyip Erdogan, Qatar’s Prime Minister Sheikh Mohammed bin Abdulrahman bin Jassim Al Thani and Palestinian Authority President Mahmoud Abbas.

The Gaza Government Media office described the deadly strike on Haniyeh’s family members on Wednesday as a “massacre” during the Muslim holiday.

“We condemn in the strongest terms the ongoing Israeli crimes against our people. In the past 24 hours, hospitals have received more than 24 people killed in cold blood by the occupation without any consideration for Muslims’ feelings,” the office said in a statement.

“We hold the US administration and the international community and the Israeli occupation fully responsible for the continuation of massacres and crimes that are being committed as part of the war of extermination and ethnic cleansing against civilians, women, children and displaced people.”