The Israeli army said Tuesday that 21 soldiers had been killed in Gaza the day before, the biggest single-day toll since the start of its ground operation on October 27.

Most of the soldiers were killed when rocket-propelled grenade fire hit a tank and a building they were trying to blow up, military spokesman Daniel Hagari said in a televised statement.

Hagari said several of the troops killed were reservists.

"We worked to find the victims until the last hours," Hagari said, indicating the difficulty in extracting bodies buried under the rubble.

"Our reservists sacrificed what was dearest to them, so that we could all live here in complete safety,” he said.

Israel began a sweeping offensive against Hamas militants in Gaza after the Palestinian group attacked southern Israel on October 7.

That attack killed around 1,140 people, mostly civilians, according to an AFP tally based on Israeli official figures.

Israel's blistering retaliatory offensive against Hamas in Gaza has killed 25,295 people, most of them women, children and adolescents.