A Russian computer programmer, Pyotr Levashov, has been arrested in the Spanish city of Barcelona, a spokesman for the Russian embassy in Madrid said on Sunday.
It was unclear why Levashov was arrested. The embassy spokesman declined to give details for his arrest, and Spanish police and the interior ministry were not available for comment on Sunday.
Russian television station RT reported that Levashov was arrested under a U.S. international arrest warrant and was suspected of being involved in hacking attacks linked to alleged interference in last year's U.S. election.
Peter Carr, a spokesman for the U.S. Justice Department's criminal division, said: "The U.S. case remains under seal, so we have no information to provide at this time."
The criminal division is separate from the national security division, which is responsible for investigating state-sponsored cyber crimes.
A U.S. Department of Justice official said it was a criminal matter without an apparent national security connection.
Spanish authorities notified the Russian embassy of Levashov's arrest on Friday, the embassy spokesman said.
In January, Spanish police arrested another Russian computer programmer, whose name was given as "Lisov" and who was wanted by the United States for leading a financial fraud network.
The U.S. government has formally accused Russia of hacking Democratic Party emails to help the campaign of Republican President Donald Trump. The U.S. Congress is also examining links between Russia and Trump during the election campaign.
Russian officials, including President Vladimir Putin, have repeatedly denied that Russia tried to influence the election.