As reported by Censor.NET citing DW, a representative of the prosecutor's office announced it on Friday, Nov. 25.
Firtash is wanted along with two accomplices, the citizens of Ukraine, whose names aren't disclosed in the interests of the investigation.
Five other accomplices directly engaged in laundering the capitals of the oligarch, including famous Spanish lawyer Antonio de Fortuny, were arrested in Barcelona and in the resort town of Marbella.
The detainees were hired by Firtash to set up a number of offshore companies in Panama, while certain amounts of money settled down in Spain after being invested in real estate.
It is about tens of millions of euros of illegal origin, according to the prosecution.
The Firtash case is probed as part of the Variola operation launched in July, 2016 with the arrest in Barcelona of Stepan Chernovetskyi, the son of former Kyiv mayor Leonid Chernovetskyi, and 11 more persons on suspicion of money laundering.
The documents found during the searches of Stepan Chernovetskyi's premises unveiled the involvement of Firtash.
However, the prosecutor's office has doubt that the Ukrainian oligarch, whose whereabouts remain unknown, will ever fall into the hands of the Spanish justice.
The Federal Bureau of Investigation has struggled to track Firtash for several years now, claiming far more serious charges, including a bribe in exchange for a license for the development of titan fields in India.
Ukraine is also trying to pick up trail of the infamous tycoon.