The protests were organized by U.S. Jewish groups including Jewish Voice for Peace, Jews for Racial and Economic Justice, and Rabbis for Ceasefire. Social media posts by the groups said 36 rabbis were at the demonstration inside the U.N. Security Council Chamber.
The Huffington Post reported that the rabbis gained access to the building as part of a guided tour.
The U.N. has demanded an immediate humanitarian ceasefire in Gaza amid the huge death toll from the war. Washington has vetoed resolutions for such calls in the Security Council, saying it would let Palestinian Islamist group Hamas, which governs Gaza, regroup and rebuild.
More than three-quarters of the 193-member U.N. General Assembly backed a move to demand an immediate humanitarian ceasefire last month.