The Islamic State group may have stolen "tens of thousands" of blank passports that it could use to smuggle its fighters into Europe as refugees, a German newspaper reported Sunday.
The Welt am Sonntag cited Western intelligence sources as saying that IS could have acquired the stolen travel documents in areas of Syria, Iraq and Libya it now controls.
The passports could be issued to would-be attackers to enter the European Union as asylum seekers, according to the report.
Moreover IS has already launched a money-spinning operation with the fake documents, selling them on the black market where they fetch up to 1,500 euros ($1,630) each, Welt said.
European authorities have repeatedly warned of the potential threat posed by refugees travelling with counterfeit documents.
The two unidentified Stade de France attackers in Paris have been tracked back to two fake Syrian passports used to enter Europe.