The UN Security Council is meeting urgently in private on Israel's military action in Gaza.
The closed session on Wednesday night comes in response to a letter from Egyptian Ambassador Muutaz Khalil.
Secretary-General Ban Ki-moon released statements saying he had spoken to Egyptian President Mohamed Morsi about "the worrisome escalation of violence in southern Israel and Gaza and the need to prevent any further deterioration."
He also said he had talked to Israeli Prime Minister Benjamin Netanyahu to express concern about "an alarming escalation of indiscriminate rocket fire from Gaza into Israel and the targeted killing by Israel of a Hamas military operative in Gaza."
AP