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The UN ordered its flags worldwide to be lowered to half-staff on Monday, with a minute of silence observed in honour of staff members who have been killed in Gaza.
The UN agency for Palestinian refugees, UNRWA, announced on Friday that 101 of its employees have been killed in the Gaza Strip since October 7.
Many of UNRWA's 13,000 staff working in Gaza are Palestinian refugees themselves.
The blue and white UN flag was first lowered at offices around the globe and later at UN headquarters in New York.
UN Secretary General Antonio Guterres observed a minute of silence at the world body's headquarters, accompanied by Deputy Secretary General Amina Muhammad.
Mr Guterres said in a tweet that this is the highest number of UN aid workers killed in a conflict in such a short time.
“They will never be forgotten,” he said.
In the lobby of UN headquarters, the names of the staffers killed in Gaza were read out as dozens of colleagues listened. Some carried white sheets with the words "Stop the fighting" and "Protect civilians."
Palestine’s UN envoy Riyad Mansour, who attended the lowering of the flag at UN headquarters earlier on Monday, urged the Security Council to call for a ceasefire.
Mr Mansour honoured UN staff for “trying to provide protection and assistance for maintaining lives for millions of Palestinians in the Gaza Strip”.
He called for an end “this occupation as quickly as possible” based on the Arab Peace Initiative.