Israel says that 13 of its soldiers have died since Saturday night in its ground offensive in the Gaza Strip.
It brings the number of Israeli soldiers killed in the offensive to 18.
Gaza suffered the highest death toll since the offensive began, with at least 87 people reported killed on Sunday – 67 of them in one area.
Palestinian President Mahmoud Abbas said the deaths in the Shejaiya district east of Gaza City were a “massacre”.
Israeli Prime Minister Benjamin Netanyahu vowed to continue operations in Gaza “as much as we need to” despite the casualties.
He said the Israeli government felt “deep pain” over deaths of its soldiers, and that Hamas, not Israel was responsible for the escalation in Gaza.
Sunday’s death toll for the Israel Defense Forces (IDF) is higher than that sustained by the IDF during the entire three-week duration of Operation Cast Lead in 2008-2009, the last time that Israel sent ground troops into Gaza.
The soldiers killed on Sunday were all from the Golani Brigade, the Israel Defense Forces said.
The deaths of so many soldiers on a single day will shock Israeli society, the BBC’s Chris Morris reports from southern Israel.
