The Islamic State of Iraq and Syria (ISIS) has posted a statement on one of its websites justifying its recent rampage of destruction of cultural heritage sites, including mosques in the Iraqi city of Mosul, the AFP reports. The statement references a hard-line form of Islam, popular among Jihadist groups, known as Wahhabism.

Sites destroyed in recent weeks have included Mosul’s Mosque of Younis, which is known as the site of Jonah’s tomb, the Shia Saad bin Aqeel Husseiniya shrine in Tal Afar and Mosul’s al-Qubba Husseiniya mosque. ISIS claims that building houses of prayer above tombs is tantamount to idolatry and must therefore be eradicated.

In the statement, an ISIS representative writes: “The demolition of structures erected above graces is a matter of great religious clarity…Our pious predecessors have done so,” adding that, “There is no debate on the legitimacy of demolishing or removing those graves and shrines.”

Followers of Wahhabist Islam believe that the use of grave sites for prayer is a form of polytheism. According to the AFP, ISIS insists in their statement, however, that Islamic law condemns the practice regardless of the follower’s sect.

The statement was published as yet more experts and scholars, both local and international, condemned the group’s destructive acts. On behalf of Iraq’s Committee of Muslim Scholars, Harith al-Dhari told the AFP, “The committee would like to underline the huge loss for  the people of Mosul, who saw these blessed mosques as landmarks of the city, a part of its culture and history.”