The European Union on Tuesday froze the assets of an Iranian intelligence unit and two of its staff, as the Netherlands accused Iran of two killings on its soil and joined France and Denmark in alleging Tehran plotted other attacks in Europe.

The move, although in part symbolic since one of the men is in prison in Belgium, marks the first time the EU has enacted sanctions on Iran since lifting a host of curbs on it three years ago following its 2015 nuclear pact with world powers.

"EU just agreed to enact sanctions against an Iranian Intelligence Service for its assassination plots on European soil. Strong signal from the EU that we will not accept such behavior in Europe," Denmark's Foreign Minister Anders Samuelsen said on Twitter.