The world has witnessed the videos of Islamic State (ISIS) members destroying ancient statues and other artifacts because they are believed to represent idolatry or pre-Islamic religions. But ISIS also is selling some antiquities to fund its operations, The Washington Post reports.

ISIS made a great show of destroying some historic sites, such as those in the city of Hatra.

Other areas ruled by ISIS, which runs like a government, are being excavated under license, with the artifacts being sold on the black market.

The group is earning tens of millions of dollars through illegal sales, the Post says. There has seen a spike in the trade since ISIS began taking over areas rich with smaller antiquities last June, Qais Hussein Rasheed, Iraq’s deputy minister for antiquities and heritage, told the Post.

"It’s a dependable source of revenue, which makes it very attractive, and it’s surprisingly untapped," Michael Danti, a professor of archaeology at Boston University, told the paper. "Over time, we’ve seen ISIL and organizations like it increase their ability to draw revenue from these crimes."

Deborah Lehr, co-founder of the Antiquities Coalition, which fights what it calls "cultural racketeering," warned collectors not to buy the items.

"The public needs to know that by purchasing these items, people are potentially funding terrorism," she said.

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