Rupert Colville, a spokesman for U.N. High Commissioner for Human Rights Navi Pillay, said his agency was watching unfolding events with "considerable alarm."
"She is appalled that once again civilians are losing their lives, including three Israeli citizens killed in their apartment by one of the hundreds of rockets fired over the past week as well as several Palestinian children, including a baby, and also a pregnant woman and some other civilians killed in Gaza," he said in a statement Friday.
The Israeli military Wednesday took credit for the slaying of Ahmed al-Jabari, commander of the Hamas military wing al-Qassam Brigades. Hamas, in response, said the Israeli side had crossed "red lines."
Colville said the high commissioner was concerned about the use of aerial attacks by Israeli forces on populated areas in the Gaza Strip. The U.S. government called for restraint during talks about the conflict this week with Egyptian leaders, but noted Israel has a right to self-defense.
The rights spokesman added that the indiscriminate shelling from Hamas-controlled Gaza Strip into southern Israel was a particular concern.