The Time reporter, Simon Shuster, has tweeted on Firtash being detained, "#Firtash has just been detained in the courthouse by Austrian police. Lawyers confirm he is now in custody."
Firtash has been detained in Vienna on a European arrest warrant, RFE/RL reported citing Austrian authorities.
A spokeswoman for Austrian prosecutors said Firtash's detention was technically separate from the extradition ruling as it was based on an arrest warrant linked to organized crime and illegal money laundering allegations in Spain.
Authorities said it was too early to tell how the implementation of the European arrest warrant would impact on the decision to extradite Firtash to the United States.
Leo Levnaic-Iwanski, who headed the three-judge panel, said the final decision will be made by Justice Minister Wolfgang Brandstetter.
As UNIAN reported earlier today, an Austrian court had ruled that Ukrainian billionaire Dmytro Firtash should be extradited to the U.S. to face corruption charges.
The judge said that since the previous Austrian court ruling the United States had offered further documents, based on witness statements, to strengthen its case against Firtash.
A U.S. grand jury indicted Firtash in 2013, along with a member of India's parliament and four others, on suspicion of bribing Indian government officials to gain access to minerals used to make titanium-based products.