Israel had a right to defend itself but needed proportionately and within the bounds of international law, foreign minister José Manuel García-Margallo said after the emergency summit.
That summit saw the UN Security Council call for an immediate ceasefire on the Gaza Strip, a message that Margallo echoed during a joint press conference with UN Assembly President John William Ashe, Spanish daily El Diario reported.
The Spanish foreign minster also said the parties involved had to work towards "the two-state solution" for the Israel–Palestine conflict by building a "safe Israel" and a "viable Palestine".
Margallo's comments come after the bloodiest day of the current crisis, with 120 Palestinians reportedly killed on Sunday, bringing the total death to over 500.
A fresh air strike on Monday morning killed a family of nine, including seven children, after a weekend of incessant shelling by land, sea and air sent thousands of terrified civilians fleeing their homes.
A man was also killed in a strike on a motorbike, taking the Palestinian death toll to 502 as the Israeli offensive entered its 14th day, medics said.