MOSCOW — The Austrian authorities have arrested a Ukrainian entrepreneur, Dmitry V. Firtash, on bribery and other charges at the request of American law enforcement agencies. Mr. Firtash has strong connections to the ousted Ukrainian president, Viktor F. Yanukovych, and also conducts extensive business in natural gas with Russia.

The Austrian federal police identified the man only as Dmitry F., a 48-year-old Ukrainian citizen, and said he was arrested Wednesday evening in a district of Vienna without incident. A government source confirmed that it was Mr. Firtash. The F.B.I. has been investigating Mr. Firtash since 2006, and an arrest warrant had been issued for him by a federal judge in Virginia, the Austrian authorities said.

The arrest comes amid political turmoil in Ukraine, with Russian forces occupying the Crimean peninsula in the south and regional officials there seeking to break away from Ukraine to become part of Russia.

In a statement, Mr. Firtash’s main company, Group DF, confirmed his arrest but called it a “misunderstanding” with no connection to the unrest in Ukraine. The company said the action in Austria was “related to an investment project dated 2006.”