Israel said it targeted Hamas' shadowy military commander in a massive strike Saturday in the crowded southern Gaza Strip that killed at least 71 people, according to local health officials. Hamas immediately rejected the claim that Mohammed Deif was targeted.Related video above — Netanyahu: Israel will not end war until all hostages return (6/27/24) It was not immediately known whether Deif was among the dead. Israeli officials confirmed that he and a second Hamas commander, Rafa Salama, were the targets. A military official later said they were "still checking and verifying the result of the strike" and did not deny it took place inside the Israeli-designated safe zone.Deif is believed by many to be the chief architect of the Oct. 7 attack that killed some 1,200 people in southern Israel and triggered the Israel-Hamas war. Second only to Hamas' top official in Gaza, Yahya Sinwar, he has topped Israel's most-wanted list for years and is believed to have escaped multiple Israeli assassination attempts in the past.In a statement, Hamas rejected the claim."This is not the first time that the occupation has claimed to target Palestinian leaders, and their lies were later proven to be false," the group said in a post on X.If Deif has been killed, cease-fire talks could be derailed by what would be seen as a major Israeli victory in the nine-month war."These false claims are merely a cover-up for the scale of the horrific massacre," Hamas said in a statement in response to Israel. The Gaza Health Ministry said at least 289 others were injured in the attack — one of the war's deadliest — and that many dead and injured were taken to overwhelmed Nasser Hospital nearby. There, Associated Press journalists counted over 40 bodies. Witnesses described an attack that included several strikes. "A number of victims are still under the rubble and on the roads, and ambulance and civil defense crews are unable to reach them," the Health Ministry said.The Israeli military asserted that "additional terrorists hid among civilians" and described the strike location as an area surrounded by trees, several buildings and sheds.Footage of the aftermath showed a huge crater, charred tents, burnt-out cars and household belongings scattered across the blackened earth. Victims were carried on the hoods and in the hatchbacks of cars, and on donkey carts and carpets.Witnesses said the strike landed inside Muwasi, the Israeli-designated safe zone that stretches from northern Rafah to Khan Younis. The coastal strip is where hundreds of thousands of displaced Palestinians have fled in search of safety, sheltering mostly in makeshift tents. "This was designated as a safe zone filled with people from the north," said one displaced Palestinian man who did not give his name. "Children were all martyred here. We collected their pieces with our hands." He estimated there were seven or eight missiles and asserted that first responders were targeted as well.At the hospital, a baby in a pink shirt, her face covered with sand, cried while receiving first aid. A small boy lay motionless at the other end of the bed, one shoe gone. Victims lay amid spattered blood on the floor, and bodies were wrapped in white plastic scrawled in marker with their names. An Israeli official said the strike was carried out within a fenced area of Khan Younis that was run by Hamas but did not elaborate on the precise location, saying it was not a tent complex but an operational compound. The official described the strike as precise and said it was estimated that many of the casualties were "terrorists."Deif has been in hiding for more than two decades and is believed to be paralyzed. One of the only known images of him is a 30-year-old ID photo released by Israel. Even in Gaza, only a handful of people would recognize him.The latest deadly strike comes as U.S., Egyptian and Qatari mediators continue to push to narrow gaps between Israel and Hamas over a proposed deal for a three-phase cease-fire and hostage release plan in Gaza. The potential killing or injury of any senior Hamas official threatens to derail the ongoing talks. The U.S.-backed proposal calls for an initial cease-fire with a limited hostage release and the withdrawal of Israeli troops from populated areas in Gaza. At the same time, the two sides will negotiate terms of the second phase, which is supposed to bring a full hostage release in return for a permanent cease-fire and complete Israeli withdrawal from Gaza. Israel launched its campaign in Gaza after Hamas' Oct. 7 attack in which militants stormed into southern Israel and abducted about 250 people.Since then, Israeli ground offensives and bombardments have killed more than 38,400 people in Gaza and wounded more than 88,000, according to the territory's Health Ministry. The ministry does not distinguish between combatants and civilians in its count.More than 80% of Gaza's 2.3 million people have been driven from their homes, and most are now crowded into squalid tent camps, facing widespread hunger. ___Federman reported from Jerusalem. Associated Press writers Jack Jeffery in Ramallah, West Bank, Fatma Khaled in Cairo and Abby Sewell and Bassem Mroue in Beirut contributed to this report.