Twenty-one Israeli soldiers were killed in combat in southern Gaza on Monday, the military said, in the biggest single loss of life for Israeli troops during the war with Hamas.

Another soldier was seriously injured in the same operation.

In a statement, army spokesman Rear Adm. Daniel Hagari said the incident took place near the Kissufim border community as Hamas attacked the soldiers attempting to destroy military infrastructure of the Palestinian resistance group.

He said the Hamas fighters fired a rocket-propelled grenade at an Israeli tank, while, simultaneously, an explosion caused two two-story buildings to collapse.

“The buildings collapsed due to this explosion, while most of the forces were inside and near them,” Hagari added.

He said an investigation had been launched into the incident as the explosion was the result of mines planted by Israeli soldiers, though the cause of their detonation is yet to be confirmed.

The army published the names of 10 soldiers, while the families of the remaining 11 were notified.

The deaths bring the death toll of Israeli soldiers in Gaza since a ground assault began on Oct. 27 to 219, while the army’s overall death toll since the launch of the Israeli offensive against Gaza on Oct. 7 has risen to 556.

Israel has pounded the Gaza Strip since a cross-border attack by the Palestinian resistance group Hamas on Oct. 7, killing at least 25,295 Palestinians and injuring 63,000. Nearly 1,200 Israelis are believed to have been killed in the Hamas attack.

The Israeli offensive has left 85% of Gaza’s population internally displaced amid acute shortages of food, clean water and medicine, while 60% of the enclave’s infrastructure has been damaged or destroyed, according to the UN. (Pieced together from reports by CNN)