The terrorist group Islamic State - Khorasan province (ISKP)* uses Ukraine as transit point for entering Western nations.
That is according to Thomas Haldenwang, the head of German Federal Office for the Protection of the Constitution.
"The ISKP managed to smuggle their supporters to Western Europe, presumably through a wave of refugees from Ukraine," Haldenwang told a press conference.
The German official said ISKP was the most dangerous among similar terrorist organizations. He recalled recent terror attacks in Western Europe, including the massacre in Bataclan Concert Hall in Paris.
"Large-scale preparatory activities are being carried out, a lot of people could be involved, weapons are being purchased, and at some of these stages the security authorities manage to put their foot in the door," Haldevang said.
German Interior Minister Nancy Faeser, who also spoke at the press conference, stressed that there are over 27 thousand jihadists and followers of radical Islam in Germany.
"Threats can come from both single jihadists and small groups, but large-scale coordinated terrorist attacks like the recent terrorist attack in Moscow are also a possible scenario," Haldevang added, referring to the terrorist attack at Crocus City Hall on March 22.
The suspects in that attack tried to flee Russia across the border into Ukraine.
* Islamic State-Khorasan Province is a terrorist group banned in Russia and many other countries.