The men, Ukrainian nationals, were arrested in Germany and Switzerland, the state prosecutor in Berlin said. They are suspected of planning to sabotage commercial freight infrastructure.
Cargo being moved at a German airport. German authorities said they were investigating three men for an alleged plot to send explosive devices to addresses in Ukraine.
Members of a group calling itself the Kingdom of Germany, which was targeted in nationwide raids, reject the existence of the German state and want to set up a parallel one.