Germany is unaware of 160 citizens whereabouts, who previously left for Syria and Iraq to join ISIS.
The ISIS member Martin Lemke from Germany was detained by Kurdish forces after he fled the last pocket controlled by terrorists.
Russian, Turkish, German leaders agreed to hold a new quadrilateral summit on Syria.
Germany has spent 48.8 million euro ($55 million) funding an opposition groups in the northwestern Syrian province of Idlib, German daily newspaper Der Tagesspiegel reported.
The summit of leaders of Turkey, Russia, France and Germany is to take place in Istanbul on Saturday, October 27. The meeting is aimed at ending the 7-year-long war in Syria.
Turkish official Ibrahim Kalın said the meeting of the leaders of Turkey, Russia, France and Germany on Syria will be held in Istanbul on Oct. 27.
The 58-old-year German artist Ursula Baher died on Tuesday in the Syrian Capital of Damascus after long suffering with cancer.
US Special Representative for Syria Engagement James Jeffrey urged Germany to participate in a joint operation against the Syrian government in case it uses chemical weapons in Idlib.
By participating in a possible strikes against the Syrian government forces Germany will violate its own constitution and human rights, the German Bundestag research service announced.
German Chancellor Angela Merkel has expressed support for Russia’s actions in Syria.