With the cooperation of the domestic intelligence agency, German police held a series of raids in different parts of northern Germany on Thursday, capturing two out of the four men they were pursuing, after threats of a suspected Islamic State militant attack in the country were received, according to Reuters.

The two suspects are Algerian and are confirmed Islamists, with one sought out by Algerian authorities for his links to IS, while the other is being held for falsification of documents, according to AFP.

"Investigations show that he has been trained militarily in Syria," German police said in a statement, AFP added.

The police also found out that the suspects were living in refugee shelters and Berlin police spokesman Stefan Redlich has assured citizens that "the refugee shelters where the suspects lived have been searched," according to an update by AFP.

Places included in the raid were four flats and two offices in North Rhine-Westphalia and Lower Saxony in Berlin, where computers, cellphones and sketches were seized, Reuters added.