UN Undersecretary of Humanitarian Affairs John Holmes advocated Israel's keeping up military pressure on the heads of Hamas, during a visit to Sderot on Sunday.
Holmes said there was "no excuse" for the Kassam rocket fire at the town, which contained no military targets. He said the real victims were the civilians, and that this was a violation of all principles of human rights.
He stressed that the children were suffering emotional damage as a result of exposure to the security threat.
Over the weekend, Holmes visited Gaza and expressed shock over the "grim and miserable" situation he encountered there, urging that the territory's borders be opened.
AP contributed to this report.