Thirteen Israeli soldiers were killed in fighting inside Gaza on Sunday, the army said, in what was the highest number of troops killed in combat since 2006.
"Over the course of the day, 13 soldiers from the IDF's Golani Brigade were killed in combat in the Gaza Strip," an army statement said.
Their deaths raised to 18 the total number of soldiers killed since Israel began a ground operation in Gaza late on Thursday, in what was the highest casualty figure since the 2006 Lebanon war.
Their deaths occurred as troops began an offensive against the Shejaiya neighbourhood between Gaza City and the Israeli border, which on Sunday claimed 62 Palestinian lives and wounded more than 250, medics said.
"We know that in battle there are casualties," Israel's Chief of Staff Lieutenant General Benny Gantz said after the news was released.
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"The residents of Shejaiya know they have fallen victim to Hamas," he said.
"We have no intention of giving up our determination."
Several media reports said seven of the soldiers were killed when their armoured personnel carrier (APC) was hit by an anti-tank missile in the early morning.
As troops tried to extract the survivors, three more were killed by gunfire.
In a second attempt to reach the scene, another three soldiers were killed by an anti-tank missile, the reports said.