Three Ukrainian men have been arrested in Germany and Switzerland for planning acts of sabotage against infrastructure in Europe on behalf of Russia, the German authorities said Wednesday.

The federal prosecutor’s office in Berlin said it was investigating the three men, who were arrested over the past five days, for a plan to send incendiary and explosive devices in parcels to addresses in Ukraine. None have been charged.

The aim, the prosecutor said in a statement, appeared to be part of a plot to damage logistical infrastructure for commercial freight. The statement did not provide further details about possible targets.