REPUBLIKA.CO.ID, MOSCOW -- Two ancient monuments in the Syrian city of Palmyra were so badly damaged by Islamic State that they can only be rebuilt using substantially new materials, Russian officials said on Thursday.

If that were to happen, many historians would view the monuments as mere replicas, shorn of the ancient heritage of the original structures.

Experts from Russia's Culture Ministry have assessed the damage in Palmyra after the UNESCO world heritage site was recaptured from Islamic State in March.

Retaking Palmyra was the first significant victory over Islamic State by Syrian forces with support from the Russian military. It was celebrated with a concert by Russian musicians in Palmyra's ancient amphitheatre a month after the battle.