(CNN) Hollywood actor Viggo Mortensen has written a letter to Spain's El Pais newspaper criticizing the far-right party Vox over its use of the character he played in "Lord of the Rings."

On April 28, Vox posted a tweet showing the party as Aragorn, played by Mortensen in Peter Jackson's film adaptation of the JRR Tolkien novel, fighting off a horde of enemies represented by the logos of LGBT rights groups, Catalonian separatists and anarchists.

The image was posted on the day of general elections alongside the caption: "Let the battle begin!"

Now the actor has written an excoriating letter to El Pais, the country's paper of record, criticizing the "ignorant" and "absurd" use of the character.

Mortensen describes himself as a "person interested in the rich variety of cultures and languages that exist in Spain and the world," and decries any implied connection with what he says is an "ultra-nationalist and neo-fascist political party."

Read More