Syria's antiquities chief has accused Turkey of refusing to return looted objects from ancient heritage sites in Syria or to provide information about them, allegations denied by the Turkish government, Sawa Radio reported.

Damascus and Ankara have been at odds since the start of a rebellion against Syrian President Bashar al-Assad in 2011, with Turkey supporting armed groups fighting Assad's government.

More recently, Daesh militants have declared a caliphate in territory they hold across Syria and Iraq and have destroyed monuments they consider pagan and sacrilegious.

One museum at the 2,000-year-old Roman city of Palmyra, a UNESCO World Heritage site the jihadi militants took over in May, has been turned into an Daesh prison and courtroom, Syria's antiquities chief Maamoun Abdulkarim said.

Even more destructive for Syria's archaeological heritage are illicit excavations at sites such as Palmyra and the even older site of Mari, near the Iraqi border, he said.

Abdulkarim said more than 2,000 objects looted from these sites had been seized in Turkey, which in contrast to other countries neighboring Syria refuses to cooperate with the Syrian authorities on documenting and returning the artifacts.

"The Turkish government refuses to register (the seized objects). There is no information, no pictures. It's not transparent," Abdulkarim said.

"They should change their approach. They told us, we cannot (do this) because our law (prohibits) us from declaring what we have," he said.

A Turkish Culture Ministry spokesman said Abdulkarim's allegations were "baseless".

"Some Syrian antiquities may have been smuggled to Turkey ... We are doing our best to prevent such smuggling," he said.

"Whenever we seize such antiquities we return them to the related country's institutions. We trained our border police on the issue very recently. I think those allegations are politically motivated," the Turkish official said.

Sources: MENA