Iran's Supreme Leader Ayatollah Ali Khamenei criticized the Saudis as unbelievers and questioned the country's role in administering the annual Muslim pilgrimage to Mecca.
"Muslims around the world should recognize the blasphemous nature of the Saudis," Khamenei said Monday in his traditional speech before the Hajj, an annual pilgrimage to holy sites in Saudi Arabia.
Starting on September 11 this year, the annual pilgrimage is a mandatory journey for every Muslim at least once in their lifetime, provided they have enough financial resources and the physical ability to undertake the journey to the birthplace of the Muslim prophet Mohammed.
However no Iranians are to take part in this year's Hajj due to a breakdown in relations with Saudi Arabia.
Khamenei said the deaths of pilgrims during last year's Hajj was further reason to question the legitimacy of Saudi control over the pilgrimage.
According to official figures, 769 Muslim pilgrims - including hundreds from Iran - died in a stampede during a Hajj pilgrimage ritual near Mecca in 2015.
Relations between Saudi Arabia and Iran have been strained since Riyadh executed a Saudi dissident Shiite cleric in January, leading an angry mob to storm of the Saudi embassy in Tehran.
Iranians mostly follow the Shia branch of Islam, while the Saudis follow the Sunni path.
Tensions between the two regional rivals have been heightened by the fact that the two support opposing sides in the Syrian civil war: Iran supports President Bashar al-Assad, while Saudi Arabia supports the rebels.