Russia has detained a US citizen in Moscow accused of spying, the FSB security service said on Monday.
It said in a statement that the American was detained on Friday "while carrying out an act of espionage" and that a criminal case had been opened.
The statement identified the American in Russian, using a name that appeared to translate as Paul Whelan.
No other details were immediately available.
The arrest came with Russia embroiled in a number of spy scandals with the West, from the alleged poisoning by Russian agents of former double agent Sergei Skripal and his daughter in England to the US conviction of Russian Maria Butina for acting as an illegal foreign agent.