A Britain-based financier who has spearheaded a United States law targeting Russian officials was briefly detained Wednesday in Spain on a Russian warrant, which authorities later said had expired.
It was carried out on a Russia-issued Interpol arrest warrant, Browder said. "Going to the police station right now", William Browder tweeted.
Spanish authorities confirmed that the anti-corruption activist was arrested in Madrid, but had since been released.
"They won't tell me which station".
In 2012, the USA passed the "Sergei Magnitsky Act" which imposed a visa ban and froze the assets of Russian officials implicated in the lawyer's death.
He wrote on Twitter: "In the back of the Spanish police auto going to the station on the Russian arrest warrant, they won't tell me which station".
He also shared a copy of the arrest warrant from the National Police Force Directorate General informing him of his right to remain silent, obtain a lawyer and call his family.More news: Xiaomi unveils Mi 8 phones, its '8th anniversary flagship'
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In March, he told The Sun the poisoning of Sergei Skripal and his daughter in Salisbury was a "Kremlin hit" because Skripal was considered a Russian traitor, adding: "Vladimir Putin has publicly said that he kills traitors wherever they are in the world".
In an image of a detention report posted by Browder himself on Twitter, police identified the reason for the detention as "fraud".
But Browder countered that, telling City A.M.:"Interpol is playing a word game - there has never been a red notice, but there have been a number of diffusion notices - it just means it hasn't been officially approved".
Minister of state at the Foreign Office, Sir Alan Duncan, said he was "deeply concerned to learn that the Russians have tried to get Bill Browder arrested in Spain".
Russian Federation was accused of trying to take advantage of the fact that Mr Browder was not in Britain or the USA, from where extradition would be more hard, a source told The Times. As far as we know, he is a British citizen now.
British Foreign Secretary Boris Johnson welcomed Browder's release, tweeting: "Just spoken to Bill Browder - very glad that he has now been released".
He was put on trial in absentia in 2013 for tax evasion - in the same trial where the deceased Magnitsky faced charges, labelled "absurd" by observers. "Moscow should concentrate on bringing those responsible for the murder of #Magnitsky to justice".