Five men have been arrested as they attempted to cross the Bulgarian-Macedonian border with decapitation videos and Islamic State propaganda on their phones. The terrorist suspects had been posing as refugees.

Bulgarian authorities near the Gyueshevo border checkpoint detained the five men, aged between 20 and 24, late on Wednesday, Bulgarian broadcaster NOVA TV reported.

The men were stopped by a border guard, who they attempted to bribe with a “wad of dollars.” However, they were searched and Islamic State propaganda, specific Jihadists prayers and decapitation videos were found on their phones.

In a move that suggests how seriously authorities are taking the case, the Bulgarian State Agency for National Security (DANS) has now taken control of the investigation under the supervision of the regional prosecutor’s office in Kyustendil.

The men chose to cross in a wooded area, local media have reported, and took a car from an accomplice who had crossed legally from Macedonia with the vehicle.

Bulgaria has recently completed a 15-foot high razor wire clad fence along 50 miles of its south-eastern border with Turkey to control the mass movement of migrants from the Middle East and Asia into Europe via the so-called Balkans route.

However, the Gyueshevo border checkpoint where the men crossed sits on Bulgaria’s western border with Macedonia. It is likely the men chose to enter there to avoid the new strict border controls on the other side of the country.

Following the recently foiled terror attack on an Amsterdam–Paris train, where the heavily armed terrorist was able to travel freely, European governments have been considering amending the Schengen border code, which eliminated systematic border controls across most of Europe.

In February, the Turkish intelligence service warned police in an internal memo that up to 3,000 trained jihadists are seeking to cross into Turkey from Syria and Iraq, who could then travel through Bulgaria and Hungry into western Europe. And in May, a Libyan government adviser warned Islamic State operatives were being “smuggled to Europe in migrant boats.”

At the time of the comments, UKIP leader Nigel Farage warned: “When ISIS say they want to flood our continent with half a million Islamic extremists they mean it, and there is nothing in this document [Common European Asylum Policy] that will stop them.

“I fear we face a direct threat to our civilisation if we allow large numbers of people from that war torn region into Europe.”