Gilgamesh Nabeel and Jabeen Bhatti

Special for USA TODAY

BERLIN — Saif Ali grew nervous when he met his six Syrian bunkmates in a Munich refugee camp after finally making it to Germany late last year.

“They were strong supporters of the Nusra Front,” said the Iraqi refugee, referring to the al-Qaeda-affiliated terrorist group fighting in the Syrian conflict. “I was praying five times a day, to hide my beliefs from them. They did not force me to, but I did not feel secure.”

Ali, 21, is an atheist and said his lack of religion was one reason he fled Iraq. He worried that if his bunkmates knew, they would consider him an apostate and beat him up — or worse.

It's a common story in Europe these days. Many refugees have detailed experiences similar to Ali’s, encountering extremists among the estimated 1 million migrants who made the journey into Europe from the Middle East last year.

After the Islamic State’s attacks in Paris in November and in Brussels in March, European concerns that terrorists could be arriving as refugees have taken on new importance, especially as more migrants arrive. Similar concerns are echoed in the United States, notably by Republican presidential candidate Donald Trump.

A survey by the Washington-based Pew Research Center released this week found about half to three-quarters of Europeans, depending on the country, said the wave of refugees raises the risk of terrorist attacks in their countries. Respondents said they fear the newcomers — even as some refugees say the same thing.

“I see many extremists,” said Bader Khaishah, 28, a Syrian refugee at a Munich refugee camp. “I cannot be certain, but they have strong tendencies (toward militancy). I can feel this from the extremist tunes on their mobile phones, their injuries and their reaction when discussing the incidents in our region.”

Frontex, the European Union's border control agency, said the Paris terrorist attacks that killed 130 people demonstrated that terrorists can mingle among the flow of migrants into Europe. "Two of the terrorists involved in the attacks had previously irregularly entered through Leros (a Greek island) and had been registered by the Greek authorities,” Frontex said in its 2016 risk analysis.

German Chancellor Angela Merkel said this week that militant groups are sneaking people into Europe among the refugees. "The refugee wave (last year) was used by some to smuggle in terrorists," she said.

Germany said it is investigating about 40 cases of suspected radicals posing as refugees. In June, German police arrested three Syrian men on allegations of planning a terrorist attack in Dusseldorf for the Islamic State. A fourth man allegedly linked to the plot is in custody in France.

Jamal Jabur, 32, an Iraqi refugee in Esslingen, Germany, said he met three men who claimed they previously fought for the Islamic State. Two of the men, from Ramadi, Iraq, were forced into the militant group, he said. But a third, from the Iraqi city of Mosul, believed in the Islamic State’s cause and often chastised anyone who didn’t follow the group’s harsh interpretation of Islam.

“The man from Mosul is a dangerous person,” Jabur said. “Once, the man from Ramadi and I talked with a German woman, and the Mosul member said this is wrong, and that prophet Mohammed disapproves.”

Jabur said he never met anyone affiliated with the Islamic State, also known is ISIS or ISIL, when he lived in Baghdad from 2003 until 2015.

"Within a few days in the refugees' camp in Germany, I met three former ISIS members," he said, shaking his head. “There are lots of them. Many are escaping the service with ISIS, but they seem to be dangerous. I felt afraid to tell the camp administration about them.”

Some extremists see their mission as converting Christians into Muslims, Ali said about a fighter from the Nusra Front militant group who was forced out of Syria after the Islamic State invaded his town.

“One of this man’s goals after getting the residence (permit) was to spread Islam. He said, 'Europe will become Muslim, we will Islamicize (them),'” Ali said.

Others who share that goal believe they are being helpful, Ali added.

"They are happy with the German attitude of welcoming other cultures and see it a suitable environment to spread Islam," he said. "They say, 'Germans are good, and we should save them.'"

Nabeel reported from Istanbul.