Mr Guterres called for a full investigation into the attacks.
“Israeli residents set fire twice to the perimeter of the UNRWA Headquarters in occupied East Jerusalem,” Philippe Lazzarini said in a post on X.
The UN General Assembly recognised Palestine as an observer state in 2012 in spite of resistance from the United States.
The Rafah border crossing remains open for aid and passenger movement, says an Egyptian source and the border authority.
The Security Council on Thursday rejected Palestine’s request for UN membership, with the United States casting a veto.
In a vote of 12 in favour, one against, and two abstentions, the council did not adopt a draft resolution recommending a General Assembly vote on UN membership for Palestine.
“I want to be very clear the strike was not carried out with the intention of harming WCK aid workers,” said chief of the general staff, Herzi Halevi.
The deaths demonstrated there was no safe place in Gaza, whether you are Palestinian, British or any other nationality, a spokesperson said.
“These are people who are angels. I served alongside them in Ukraine, Gaza, Turkey, Morocco, the Bahamas, and Indonesia.’’
A resolution in the UN Security Council requires at least nine of the 15 votes to pass, and there can be no veto from one of the permanent five powers.
