* Detained in Vienna at request of U.S. authorities
* Dmytro Firtash is one of Ukraine's richest men (Adds details and background)
VIENNA, March 13 (Reuters) - Austria has arrested Ukrainian businessman Dmytro Firtash at the request of the United States which has been investigating him since 2006, government sources said.
The Federal Crime Agency on Thursday identified the suspect only as Dmitry F., 48, but government sources said it was Firtash, one of Ukraine's richest men.
"Based on years of investigations by the U.S. FBI and an arrest warrant issued by a U.S. federal district court, Vienna prosecutors issued a national order to detain the businessman," the agency said in a statement.
It said he was suspected of violating laws on bribery and forming a criminal organisation in the course of foreign business deals. A spokesman for the agency said the Austrian order to take him into custody came this month.
Firtash's close links to Russia and involvement in the gas, chemicals, media and banking sectors gave him substantial influence, notably during the administration of recently ousted, Moscow-backed President Viktor Yanukovich.
The suspect was taken into custody without incident in Vienna on Wednesday evening, a statement said. He was transferred to a justice facility in Vienna after the arrest.
Firtash is founder and chairman of Group DF, whose website describes it as a diversified international group of companies operating across Europe and Asia in fields including fertiliser, titanium, gas distribution and banking.
Other businesses include agribusiness, media, soda ash production, energy infrastructure development and real estate.
Firtash is not named on an initial European Union list of Ukrainians suspected of misusing state funds and violating human rights and whose assets are to be frozen as a result of the crisis over the Russian takeover of Ukraine's Crimea region.
There was no immediate comment from the FBI or U.S. Justice Department. (Reporting by Michael Shields and Angelika Gruber; Editing by Janet Lawrence)
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