LONDON — The authorities in Germany announced on Thursday that they had arrested a 23-year-old Syrian who is suspected of working for the Islamic State’s news agency, which announces claims of responsibility for the group’s attacks, including the most recent ones in London and Tehran. 

According to a statement from the federal prosecutor’s office, the Syrian — a man identified only as Mohammed G., who was arrested on Wednesday — arrived in Germany in September 2015. “ Once he arrived, he acted as a contact person between the news agency Amaq, which is considered part of Islamic State, and possible assailants of the terror organization,” the statement said. 

If proved, the presence of a member of Amaq in Western Europe would help answer a riddle: How is it that the Islamic State has continued to run a media empire, one that rapidly turns to social media to issue claims of responsibility for attacks, despite its losses of territory in Iraq and Syria? 

Analysts had long suspected that the Islamic State, also known as ISIS or ISIL, had media operatives on different continents and across time zones, both because of the rapid response of its statements and because its claims are frequently translated into numerous languages, including German.