Saudi Arabia's top cleric said Iranians are "not Muslims" in response to Iranian Supreme Leader Ayatollah Ali Khamenei's criticism of the Saudis' handling of the hajj pilgrimage.
Grand Mufti Abdul-Aziz al-Sheikh told the daily Makkah newspaper on September 6 that Iranians are descendants of Mujaws, a reference to Zoroastrians and others who worship fire.
He added that Iranians' "hostility towards Muslims," particularly Sunnis, "is an old" thing.
Iranians are predominantly Shi'a Muslim.
Sheikh's comments come one day after Khamenei said Saudi Arabia's management of the Islamic holy sites of Mecca and Medina should be challenged by the Muslim world.
The heated words between the two Mideast rivals come just a few days before the September 10 beginning of the hajj.
Khamenei wrote on his website that "Saudi rulers" had shown "oppressive behavior" toward hajj pilgrims and because of that should reconsider who manages Mecca and Medina.
At least 2,297 pilgrims were killed in a stampede at the hajj in 2015, with Iranians making up the bulk of the victims.
Iran said it is not sending any pilgrims on the hajj this year after talks with Saudi officials about security failed.