Story highlights Kremlin releases footage which suggests ISIS ready to raze parts of historic Syrian city

Militants have destroyed much of Palmyra since occupying it in May 2015

(CNN) ISIS' vandalism of one of Syria's most important historic sites looks set to escalate as Russian intelligence suggests that the militant group plans to wreak more destruction on the ancient Roman ruins at Palmyra.

The city has seen many of its irreplaceable antiquities, monuments and historic sites destroyed since the terror group first occupied it in May 2015.

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Russia's Defense Ministry released a statement Monday saying they have detected "an upsurge in truck movement" near the ancient site that indicates that ISIS is planning to cause even more damage to the ancient complex.

"We have detected an upsurge in truck movement near the ancient city amid Syrian troops' successful advance on Palmyra," the statement reads. "This indicates that Daesh (ISIS) wants to bring in explosives to deal maximum damage to the remaining architectural relics before they leave."