Speaking at a joint press conference with Benjamin Netanyahu, UN Secretary General Ban Ki-moon says "further escalation would be dangerous and tragic for the entire region. Civilian casualties are unacceptable under any circumstances."
Mr Ban is taking gentle swipes at Mr Netanyahu, blaming Israel for "unacceptable" civilian deaths."
He added: "The world is watching and waiting" for peace in Gaza."
Today's bombing in Tel Aviv is reminiscent of six years ago and could mark a serious escalation in the conflict.
A truce in Gaza suits all sides but none of the groups seem interested in a long-lasting solution.
A complex system of air defences has been instrumental in protecting Israel's population from incoming rockets.