Archaeological sites in Syria are being looted "on an industrial scale," with proceeds being used to fund Daesh extremists, the head of UNESCO chief warned on Wednesday.

"Satellite imagery shows that archaeological sites in Syria are dotted by thousands of illegal excavations ... that show there is looting on an industrial scale," Irina Bokova was quoted as saying in press statements in Sofia.

"Limiting the trafficking in cultural property is a top priority because it finances the actions of the extremists," she told a news conference.

"The world expects from us to undertake decisive and uncompromising action ... to stop this source of funding for the extremists."