An ISIS statement released late Thursday said the six busts were found when the smuggler was stopped at a checkpoint. The issue was referred to an Islamic court in the northern Syrian town of Manbij, which ordered that they be destroyed and the man be whipped.

Photographs released by the group showed ISIS fighters destroying the busts with large hammers. Another photo showed the smuggler being whipped.

The UK-based Syrian Observatory for Human Rights said on Friday it was unclear if the busts were authentic or if the militants destroyed fake busts as a cover for the ISIS group’s own antiquities smuggling.

While there is no firm evidence of the amount of money being made by ISIS from looting antiquities, satellite photos and anecdotal evidence confirm widespread plundering of archaeological sites in areas under the militant group’s control.

ISIS captured the historic Syrian town of Palmyra in May from government forces. Many fear that the group will damage the town’s archaeological sites as they did in neighboring Iraq earlier this year.

Palmyra’s UNESCO world heritage site is famous for its 2,000-year-old Roman colonnades, other ruins and priceless artifacts. Before Syria’s conflict began in 2011, tens of thousands of tourists visited the remote desert outpost, a cherished landmark referred to by Syrians as the “Bride of the Desert.”

In March, ISIS members in Iraq razed 3,000-year old Nimrod and bulldozed 2,000-year old Hatra – both UNESCO world heritage sites.

The Sunni extremists, who have imposed a violent interpretation of Shariah law in the territories they control in Syria and Iraq, believe ancient relics promote idolatry.

ISIS militants also recently destroyed a lion statue dating back to the 2nd century in Palmyra, said Maamoun Abdulkarim, the head of the Syrian government’s Antiquities and Museums Department.

He said the statue, discovered in 1977, had stood at the gate of the town’s museum, and had been placed inside a metal box to protect it from damage.