FILE PHOTO: Ukrainian oligarch Dmytro Firtash arrives at court in Vienna, Austria, February 21, 2017. REUTERS/Heinz-Peter Bader/ File Photo

VIENNA, Dec 10 (Reuters) - An Austrian court has dealt a final blow to U.S. attempts to extradite Ukrainian tycoon Dmytro Firtash to face trial on corruption charges, rejecting an appeal against a ruling blocking the move.

Firtash made a fortune selling Russian gas to Ukraine. Once a supporter of Ukraine's ousted pro-Russian president Viktor Yanukovich, he has fought the attempted extradition from Austria in the courts for years.

A U.S. grand jury indicted Firtash in 2013, along with a member of India's parliament and four others, in a case in which Firtash was accused of bribing Indian government officials. Firtash denies wrongdoing.

"In its ruling of December 9, 2025, the Vienna Higher Regional Court dismissed the prosecutors' office's appeal against the ruling of the Vienna Regional Court for Criminal Matters of November 4, 2024 as inadmissible," the Vienna appeals court said in a statement issued on Wednesday.

It was referring to a lower court's ruling that Firtash could not be extradited to the United States. It said its ruling was final and could not be appealed.

While the Austrian courts will not allow his extradition to the U.S., what he will do now is unclear.

Firtash is wanted by Ukrainian and U.S. authorities on suspicion of embezzling nearly $500 million involving Ukraine's gas transit system. Britain said last year it was barring him from the country and freezing his assets as part of a crackdown on 'dirty money'. It also imposed sanctions on his wife, Lada.

Firtash says the charges are without legal foundation.

(Reporting by Francois Murphy and Alexandra Schwarz-Goerlich; Editing by Alexandra Hudson)