"I utterly condemn this latest horrendous ISIL atrocity, targeting innocent civilians who were celebrating Ramadan in the heart of Baghdad," Zeid Ra'ad Al Hussein said in a statement.
His statement comes in the wake of deadly suicide car bomb attacks which hit Baghdad on Sunday. At least 166 civilians were killed by the Islamic State-claimed attacks, with the death toll expected to rise as many of the wounded are in critical condition.
The bloody bombings have been claimed by the Islamic State (IS, or ISIL) group which said that one of its suicide bombers detonated his car bomb at a crowd of Shiite people in the predominantly Shiite district of Karrada-Dakhil, according to a statement posted online, which could not be independently verified.
The High Commissioner warned that efforts to defeat ISIL must be in line with international law, since heavy-handed responses all too often create resentment amongst targeted populations, facilitating both the recruitment and propaganda carried out by extremist groups such as ISIL.
"The way we react, in Iraq and elsewhere, will in many ways decide whether ISIL benefits from its indiscriminate acts of mass murder, or is ultimately destroyed by them," highlighted Zeid.
In light of this, the official called for the immediate release of over 600 men and boys reportedly taken captive by a militia group involved in the recapture of Fallujah from ISIL last month.