Cardinal Jean-Louis Tauran, the chair of the Roman Catholic church's council for interfaith dialogue, said he had been profoundly shocked by accounts of the horrific death of Shehzad Masih and Shama Bibi.
Shehzad, a bonded labourer, and his pregnant wife were beaten by a mob of 1,500 people then thrown on top of a lit furnace on Tuesday in a crazed reaction to rumours they had thrown pages of the Koran into the garbage.
"How can we remain impassive before such crimes, justified in the name of religion?," Tauran said on Vatican Radio, urging Muslim leaders in Pakistan to vigorously condemn the killings.