Pakistan Ulema Council's (PUC) condemnation came just a few days after Tehreek-i-Taliban Pakistan's (TTP) six top commanders pledged allegiance to the IS leader Abu Bakr al-Baghdadi, who has declared a "caliphate" in areas the group controls in Iraq and Syria.
"Islam and Muslims cannot support the killing of innocent people and destruction of their properties by the IS. We appeal to people and youth in Islamic countries to stop cooperation with the violent group," PUC said in a statement.
It said that IS violates the teachings of Islam in Iraq and Syria where its controls large swathe of territory.
On October 14, Taliban's spokesman Shahidullah Shahid along with five senior rebel leaders announced allegiance to the IS group.
The condemnation came as the local media reported incidents of wall chalking in support of the IS group in the southern port city of Karachi. Earlier, its pamphlets were distributed in northwestern city of Peshawar.