Historic sculptures and other artefacts have been removed from Syria's National Museum in Damascus, authorities report.
The robbery was noticed on Monday, when staff allegedly found that an entrance had been broken from the inside.
The six missing pieces were crafted from marble and originated to the Roman era, one official told the media outlet.
Cultural heritage officials said it had launched a probe to establish the "events surrounding the theft of a number of exhibits", and that measures had been implemented to improve safeguarding and surveillance.
The chief of internal security in Damascus province, General Osama Atkeh, was quoted by the government press as saying that authorities were investigating the robbery, which he said had targeted several "ancient sculptures and valuable objects".
He noted that security personnel at the museum and additional people were being interviewed.
The cultural institution, which was created in the early twentieth century, holds the most important cultural treasures in Syria.
It features historical records dating back to the Bronze Age from Ugarit, where proof of the most ancient linguistic system was uncovered; 1st and 2nd Century AD Greco-Roman sculptures from the ancient city, among the foremost ancient sites of the ancient world; and a third century Jewish temple that was established at another archaeological site.
The facility was compelled to shut in 2012, twelve months after the outbreak of the devastating civil war. A large portion of the holdings was evacuated and preserved at secret locations to safeguard them.
It partially resumed in 2018 and resumed full operations in the beginning of the year, a month after rebel forces removed the Assad regime.
Every one of Syria's Unesco World Heritage sites were damaged or partially destroyed during the conflict.
The IS organization blew up numerous temples and other structures at Palmyra, stating that they were against their beliefs. Unesco condemned the destruction as a violation.
Countless historical objects were also damaged or looted from dig sites and collections.
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