The military wing of Hamas said on Sunday that the commander of its northern brigade and four other senior leaders had been killed during Israel's offensive in the Gaza Strip.
In a statement, the Ezzedine Al-Qassam Brigades said Ahmed al-Ghandour was a member of its military council, and named three of the others, among them Ayman Siyyam, head of its rocket division, while its West Bank branch confirmed another leader's death.
"We pledge to Allah we will continue their path and that their blood will be a light for the mujahedeen and a fire for the occupiers," the statement said, without saying when they were killed.
The Israeli army said it had killed "five senior commanders".
It claimed Ghandour was "a leading figure in the planning and execution of the October 7 massacre" when Hamas carried out a surprise attack in Israel, killing 1,200 Israelis and took around 240 captive.
Israel has bombarded residential buildings, hospitals, refugee camps and schools. Rights groups and several countries have described Israel's actions as war crimes.
Israel has gone on to bombard residential buildings, hospitals, refugee camps and schools, while rights groups and several nations have gone on to describe Israel's actions as war crimes.
Multiple entities have called for a permanent ceasefire, though a four-day truce - now in its third day - was what was agreed upon.
The army claimed that Ghandour headed one of the Hamas military wing's five regional brigades in the Gaza Strip.
He was "responsible for directing all Hamas's terror activities" in northern Gaza.
It identified Siyyam as a senior figure who headed Hamas's rockets division for "approximately 15 years".
Wael Rajab, described as Ghandour's deputy and the former police chief in northern Gaza, had also been killed, it said, as had Raafat Salman, a senior operative in Qassam's Gaza City Brigade involved in planning the motorised glider infiltration on October 7.
The fifth dead commander, Farsan Khalifa, was a senior operative with Hamas's West Bank headquarters who "aided and was close to" its Gaza leadership, it added.
The Israeli army said Ghandour, Siyyam and Khalifa were killed in the same strike, without saying where or when it took place.
Last week, a senior Israeli military official said troops had killed "more than 50" Hamas commanders causing "significant" harm to the capacity of the military wing, which the official estimated to have around 24,000 fighters.
Ghandour - whose nom de guerre was Abu Anas - was put on a US economic sanctions blacklist in 2017 as a "global terrorist".
The State Department said at the time he was a member of Hamas's political bureau, as well as a former member of its Shura council, which groups its leaders from Gaza, the West Bank and overseas.
It said he had been involved in "many terrorist operations" including a 2006 attack on the Kerem Shalom border crossing which killed two Israeli soldiers and wounded four others and led to the kidnapping of Israeli soldier Gilad Shalit, who was held by Hamas for five years.
He was freed in 2011 in exchange for 1,027 Palestinian prisoners.
The senior Israeli military official claimed that troops had caused significant damage to Hamas's fighting force, notably in the north.
"In some (battalions), we eliminated hundreds of Hamas terrorists and most of the battalion commanders," he said.
"This harm is significant, it dismantles the ability of Hamas to fight right now, but also the ability to rehabilitate its military power after the war."
He did not give a number of militants killed but said it was in the several thousands: "not 10,000, not 1,000, something in the middle".
The Hamas announcement Sunday came on the third day of a four-day pause in the fighting during which Hamas has handed back 26 Israeli hostages, all women and children, in two batches as well as 15 foreign nationals, mostly Thais.
In return for the Israeli hostages, Israel has freed 78 Palestinian prisoners, all of them women and teenagers.
A further 13 Israelis and four foreign nationals were released on Sunday, with 39 Palestinian women and children expected to be freed later on the day.
The truce has offered some respite in war-hit Gaza, though fears are mounting for when the ceasefire comes to an end, as Prime Minister Benjamin Netanyahu has vowed to continue until Israel is "victorious".