Customs police detained the suspect, German national Alexander S., in the Bavarian city of Augsburg on Tuesday, federal prosecutors said in a statement.

He stands accused of violating the foreign trade law by entering into commercial deals "with the secret service of a foreign power", they said.

In connection with the probe, officers raided the suspect's Augsburg apartment as well as business premises in Bavaria, Saxony state and Berlin.

As the managing director of a company based in southern Germany, Alexander S. is alleged to have sold machine tools to "military end users" in Russia.

He allegedly bypassed checks by listing bogus recipients for his goods. He also fraudulently obtained the necessary export permits by giving "incorrect information" about how the goods would be used.

The accused carried out seven such transactions between January 2016 and January 2018 worth a total of some eight million euros ($8.7 million), prosecutors said.

The European Union imposed sanctions on Russia following its annexation of Crimea in 2014.

They include a ban on exporting "dual-use goods and technology" that can be used for both military and civilian purposes.