More than 10,000 original, blank passports had been seized by the terror militia "Islamic State" (IS) since last year when it captured Syrian and Iraqi towns, German weekly "Welt am Sonntag" reported on Sunday quoting Western intelligence services.

The militant groups, the newpaper reported, has used "real fake documents" to earn money, with the identity papers selling for up to $1,500 on the black market. Intelligence officials fear the documents could be used by terrorists seeking to enter Europe.

Separate reports last Monday said the number of migrants traveling to Germany with fake Syrian passports was at 8 percent far smaller than the Interior Ministry had once implied.

Frontex: 'Security risk'

"Welt am Sonntag" quoted Fabrice Leggeri, who heads the EU's external border agency Frontex, as saying that "uncontrolled" migrant inflow into Europe "naturally represented a security risk."

Frontex officials checked whether asylum seekers arrived with fake or stolen papers but their informative value was "very scant" because no one could guarantee that passports from a war-torn land such as Syria were officially issued, Leggeri told the paper.

"Welt am Sonntag" said an unnamed foreign intelligence service had recently sent German authorities a list of numbered blank passports stolen by the IS in the Syrian areas of Raqqa and Deir al-Sor as well as the Iraqi regions of Anbar, Ninive and Tikrit.

That data has since been transferred into the database for the EU's passport-free internal Schengen zone, the paper added, to help avert infiltration into Europe of further potential attackers.

Two Paris attackers

In late November, French prosecutors said two of the seven attackers who died during and after the November 13 attacks in Paris remained unidentified despite carrying Syrian passports showing that he had entered the EU via Greece in October.

More recently, Austrian police arrested two suspects at a migrant hostel in Salzburg and found them to be carrying passports consistent with the same tranche from Raqqa.

Focus also on European passports

"Welt am Sonntag" added that two IS suspects arrested by Turkey last Thursday while carrying nearly 150 original European passports were of Belgium-Turkish origin.

The suspects were detained at Istanbul's main airport after they had flown in from Europe.

The private Turkish news agency Dogan said the documents were hidden inside "five mini pizza ovens." Two hidden cameras, scores of memory and SIM mobile phone cards were also seized, it added.

Interior Minister Efkan Ala said Turkey had imposed entry bans on 33,746 suspects from 123 countries since the Syria conflict began in 2011. Turkey is often used as a transit country for people leaving Syria for Europe and for others trying to get into Syria, sometimes to fight for Islamic State or other militant groups.

Syria requires visas

Also on Thursday, Syria said it would begin requiring visas from Turks entering the country, negating visa-free travel that had been in place since 2011.

Turkey currently has at least 2.2 million Syrian refugees, many of them dependent on low paying jobs.

ipj/sms (AFP, Reuters, dpa)