Russian computer programmer Pyotr Levashov has been arrested in the Spanish city of Barcelona.
It is unclear why Levashov was arrested. A spokesman for the Russian embassy in Madrid declined to give details for his arrest, and Spanish police and the interior ministry were not available for comment.
Russian television station RT reported that Levashov was arrested under a US international arrest warrant and was suspected of being involved in hacking attacks linked to alleged interference in last year's US election.
Peter Carr, a spokesman for the US Justice Department’s criminal division, said the case was under seal so the agency was unable to comment.
The criminal division is separate from the national security division, which is responsible for investigating state-sponsored cyber crimes.
A US 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 US government has formally accused Russia of hacking Democratic Party emails to help the campaign of President Donald Trump. The US 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.