German olice arrest
German police arrest an Algerian immigrant in Berlin as part of anti-terror raidsGetty

Isis militants are entering Europe disguised as refugees, the chief of Germany's domestic intelligence said. It follows the arrest of a 35-year-old Algerian allegedly planning terror attacks who entered the country posing as a refugee in 2015.

Hans-Georg Maassen said that the Paris attacks showed that Isis was disguising terrorists as refugees so they could enter Europe. At least two of the perpetrators of the attacks entered Europe through Greece in 2015 among refugees flowing into Europe.

"We have repeatedly seen that terrorists ... have slipped in camouflaged or disguised as refugees. This is a fact that the security agencies are facing," Maassen told ZDF television. "We are trying to recognize and identify whether there are still more IS fighters or terrorists from IS that have slipped in," he added.

On Thursday, 4 February, German police arrested an Algerian man and his wife at a shelter for asylum applicants in North Rhine Westphalia, while a 49-year-old Algerian man was arrested in Berlin. Berlin police said the man, who posed as a refugee, received military training in Syria. The group was planning to commit terror attacks in Berlin, German media reported.

On Thursday (4 February) the woman who tipped French police off about the whereabouts of Paris attacks planner Abdelhamid Abaaoud said that the Belgian extremist had bragged about the ease with which he was able to enter Europe with false documents. He said that 90 jihadists, including Britons, entered France with him. Abaaoud was killed in a shoot-out with police days after the Paris attacks of 13 November.

Maassen warned against panic. "We are in a serious situation and there is a high risk that there could be an attack. But the security agencies, the intelligence services and the police authorities are very alert and our goal is to minimize the risk as best we can," he said.