VIENNA (REUTERS) - The Ukrainian businessman arrested in Vienna this week at the request of US authorities is Dmytro Firtash, Austrian government sources said on Thursday.

Firtash, 48, is one of Ukraine's richest men, an oligarch whose 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 Federal Criminal Office, had identified the man taken into custody only as Dmitry F. and said he had been under investigation by the US Federal Bureau of Investigation since 2006.