The Israeli army says 24 of its soldiers were killed in Gaza on Monday - the deadliest day for its forces since their ground operation began.
That includes 21 reservists who died in an explosion likely caused by mines that Israeli forces had placed in two buildings to demolish them, the Israeli Defense Forces (IDF) said.
It is thought a missile fired by Palestinian armed fighters hit a tank near the buildings.
The IDF is investigating what happened.
Its chief spokesman, Rear Admiral Daniel Hagari, said the reservists were killed in central Gaza at around 16:00 (14:00 GMT) on Monday - close to the kibbutz of Kissufim on the Israeli side of the border.
He said they were involved in an operation to allow for residents of southern Israel to safely return to their homes after tens of thousands were evacuated after the Hamas attack on 7 October.
On Monday, Israel's military had already confirmed that three officers were killed in a separate attack in southern Gaza.
Israeli Prime Minister Benjamin Netanyahu described the deaths on Monday as "one of the most difficult days since the war erupted".
"In the name of our heroes, for the sake of our lives, we will not stop fighting until absolute victory," he wrote on X, formerly Twitter.
Israeli President Isaac Herzog said it had been an "unbearably difficult morning" learning about the extent of the death toll.
"On behalf of the entire nation, I console the families and pray for the healing of the wounded," he said.
Israel launched the war with the declared aim of destroying Hamas after waves of its gunmen killed 1,300 people - mostly civilians - and took about 250 others hostage in the unprecedented attack.
According to the IDF website, 217 soldiers have been killed since the beginning of Israel's ground invasion on 27 October out of a total of 545 killed since 7th October.
At least 25,295 people - mainly woman and children - have been killed in the Israeli military campaign in Gaza since then, according to the Hamas-run health ministry.
