Anti-immigration campaigners have warned for some time that a small number of jihadists were traveling covertly among the millions of legitimate refugees plying the migrant route to Europe.

At least two of the Paris attackers took the Balkan route before carrying out atrocities in the French capital last November, local media reported at the time.

Further evidence of the Islamist intrusions was revealed on Thursday when German police arrested three Syrians suspected of plotting to carry out an attack on the western German city of Düsseldorf.

At least two of the men traveled to Turkey before moving separately through Greece and heading for Germany via the Balkans in March and July of last year. The terror plot only came to light when a fourth suspect blew the whistle, after he had turned himself into authorities in Paris in February.

While EU states have attempted to tighten up the refugee registration process, Brussels, along with the German government, is likely to face renewed criticism that current controls are still allowing suspected "IS" militants to enter the continent, posing as refugees.

Boosts xenophobic narrative

For many of Germany's newest residents, the roughly 1.2 million people who arrived in the country over the past year, Thursday's thwarted terror plot has reignited fears about migrant stereotyping.

"We are talking about just a few people arriving every month or so who destroy the reputation of refugees here," Iraqi national Mustafa Ahmed Hussein told DW, in Arabic through a translator.

Hussein, whose first perilous attempt to cross the Mediterranean was thwarted when the boat he was traveling in was intercepted by EU border authorities, is now studying in the western Germany city of Bonn. After being arrested and returned to Turkey, he was able to make a second crossing to Greece and eventually made it to northern Europe.

Better filters required

Hussein told DW that while most migrants are keen to integrate into German culture, there are some who remain unwilling to blend in, which could lead to a greater suspicion of all refugees.

"They come here under the guise of being refugees. But perhaps they are criminals; perhaps they are wanted (in their home country). And it's difficult for us, as refugees, to tell who is who," Hussein said.

He urged German authorities to step up counterterrorism efforts along the remaining open migrant routes.

After details of the latest thwarted terror plot were revealed, German police union chief Rainer Wendt warned that the strategy of "IS" sought to discredit entire groups and sow fear among the German population.

He told the German news agency DPA that "we must push back against this."

Syrian Delshan Ali, who has been in Germany for nine months, is also concerned that the Düsseldorf terror plot may impact on genuine asylum-seekers.

"It turns into a stereotype. Everybody will look at the refugees and say "they're criminals, they're terrorists," which is unacceptable, and it hurts me," she told DW, also in Arabic through a translator.

Ali, who is of Kurdish origin, says she considers Germany to be her final destination, unless a regional Kurdish state becomes reality.

In addition to jihadists with plans to strike Europe, some extremists who have already committed atrocities in Syria and elsewhere may be covertly seeking refuge in Germany, she suspects.

Fears for asylum cases

Iranian national Amir Ali Puramjat, who is also of Kurdish origin, made the journey to Europe roughly 11 months ago. He told DW he didn't witness any extremist talk during his travels.

He said it was important not to tar all migrants with the same brush, adding that Europeans needed to better understand the different struggles in the Middle East.

"The Kurds don't carry out attacks outside their homeland. It's an internal conflict in the mountains. We would never bring our conflict to another country," Puramjat told DW.

Speaking Farsi through an interpreter, he said he was still waiting for his claim for political asylum to be approved, after having attended court and being interviewed twice by German authorities.

Adding to fears that Thursday's revelations are giving political ammunition to anti-immigration groups and the far-right, Puramjat said, "If these extremists are going to reduce my chances of a successful asylum case, then that is unfair."