Staggering number of Europeans joined terror groups, says EU

The European Union's border agency has said it cannot fully track the flood of refugees pouring through its borders, as a "staggering number" of Europeans join terror groups, and many try to return to the continent as asylum seekers.

Europe reported a record 1.82 million illegal border crossings last year, according to Frontex, but the group conceded that the true number of illegal crossings is probably higher because so many refugees have entered Europe undetected.

"The Paris attacks in November 2015 clearly demonstrated that irregular migratory flows could be used by terrorists to enter the EU," the Fox News quoted the report as saying. "With no thorough check or penalties in place for those making such false declarations, there is a risk that some persons representing a security threat to the EU may be taking advantage of this situation."

Two extremists involved in the Paris attacks entered through the Greek island of Leros and registered with Greek authorities using fraudulent Syrian documents, The Telegraph reported. The route through the Greek islands accounted for the largest number of detections - more than 885,000.

"There is no EU system capable of tracing people's movements following an illegal border-crossing. Therefore it is not possible to establish the precise number of persons who have illegally crossed two sections of the external borders of the EU," the report stated.

Austria's Interior Minister Johanna Mikl-Leitner and Germany's Interior Minister Thomas de Maiziere said Tuesday the EU must link efforts to control migration and improve security by establishing functioning outer borders and improving information exchange channels among its member nations over terror threats, Fox News reported.

"A Europe without internal borders can exist only when a European outer border" functions to control those entering the EU, Mikl-Leitner said. Citing figures of 5,000 radicals in Europe, she said the EU needed "systematic border controls ... where EU citizens first and foremost are the ones controlled."

De Maiziere also focused on the need for all EU nations to work together to reduce the threat of new terror attacks.

The European Union began sending back refugees Monday under an agreement with Turkey.