In a statement on Tuesday, German Interior Minister Thomas de Maiziere said three Syrian nationals identified as 17-year-old Mahir Al-H., 26-year-old Mohamed A., and 18-year-old Ibrahim M. were arrested earlier that day during pre-dawn raids.

The full names of the suspects have not been released due to Germany's privacy laws.

According to German news agency DPA, police raids were carried out at asylum seeker shelters in the towns of Ahrensburg and Großhansdorf and Reinfeld in the northern German state of Schleswig-Holstein.

Over 200 officers from the German Federal Police and agents from Germany's GSG 9 special operations unit were involved in the operation.

Labeling the trio a "possible sleeper cell," De Maiziere said on Tuesday that the three suspects were smuggled out of Syria by the same organization used by members of the Paris group who carried out the November 2015 terrorist attacks.

"There is every reason to believe that the same trafficking group used by the Paris attackers also brought the three men who were arrested to Germany," he said, adding that their forged travel documents came from "the same workshop."

Training in Syria

According to the investigation so far, the three came to Germany in November 2015, with the intention of "carrying out a previously determined order [from IS] or to await further instructions."

The prosecutor's office said, however, that the investigation had not yet uncovered any concrete orders or instructions for attacks that had been given to the suspects.

Mahir Al-H. is believed to have received training from IS in Raqqa, Syria, on how to use weapons and explosives in September 2015. One month later, he and the other two suspects are believed to have agreed on a plan to travel to Europe to carry out operations or attacks outside of IS-controlled areas.

For the purposes of their travel, prosecutors say they were given passports by IS, along with cash in US dollars "in a high four-figure sum" and mobile phones pre-loaded with a communications program. The trio then left Syria last October and travelled via Turkey and Greece - a route used by tens of thousands of refugees and migrants.

De Maiziere said German police had monitored the men for months and tapped their phones, meaning that at no stage was there a risk of an attack.

Concerns over hidden jihadis

According to the BKA, authorities have received 415 leads on refugees with a terrorist background, but most have proven to be unfounded. Sixty-three investigative proceedings have been launched based on the information the BKA has received.

German authorities have repeatedly urged the public not to confuse migrants and "terrorists." Berlin has acknowledged, however, that more jihadists may have entered the Germany among the one million asylum seekers who arrived last year.

De Maiziere reiterated on Tuesday that "it would be wrong to place refugees under general suspicion."

"Security forces have repeatedly received tip-offs of individual terrorists or sympathizers among the refugees ... but most of these have turned out not to be true," he said.

Germany remains on edge following several violent incidents in July, including a suicide bombing close to a music festival, an ax-and-knife attack on a commuter train and the Munich shopping mall shootings, which left 10 people dead.

Several of the incidents were carried out in the name of IS, which has led to concerns the country could soon be the target of a major attack.