"The UN remains in close contact with all parties to solidify the ceasefire and ensure that the significant progress made towards easing restrictions, which we have seen since the end of the escalation last May, can be safeguarded and ultimately expanded," Wennesland said at a briefing to the UN Security Council.
He noted that the recent escalation in the region "took a severe toll on the civilian population."
"I repeat, the figures we are presenting are initial and verification is ongoing," he added.
Late on Sunday night, the Israel Defense Forces (IDF) said that air raid sirens sounded in southern Israel after the ceasefire took effect. The Jerusalem Post reported that multiple rockets were fired toward southern Israel minutes after the truce with the Palestinian Islamic Jihad group went into effect.
The IDF launched an operation dubbed Breaking Dawn against Islamic Jihad in the Gaza Strip on Friday. Prime Minister Yair Lapid said on Sunday that the objectives of the Breaking Dawn operation had been achieved.
On Friday, the IDF confirmed that a senior Islamic Jihad commander in northern Gaza, Tayseer Jabari, was killed in an Israeli airstrike that day. Another high-ranking commander, Khaled Mansour, was killed in an Israeli airstrike in the city of Rafah in the Gaza Strip on Saturday night.