Russia's domestic security service (FSB) said on Monday it had detained an American citizen suspected of spying in Moscow.

The FSB, said in a statement last Friday that the U.S. citizen had been detained under Article 276 of the Russian Criminal Code, which allows for sentences of up to 20 years in prison, and a criminal case had been opened against him.

The U.S. citizen, known as Paul Whelan according to the statement, was detained over spying three days ago in Moscow. No details were provided regarding the nature of the alleged espionage.

The U.S. Embassy in Moscow could not immediately be reached for comment.

The arrest came with Moscow embroiled in a number of spy scandals with the West and after President Vladimir Putin accused Western nations of using espionage cases to try undermine an increasingly powerful Russia.

Russia's relations with the United States have soured since Moscow incorporated the Crimean peninsula from Ukraine in 2014. Since then the United States and other Western countries have imposed a wide range of sanctions against Russian officials, companies and banks.

(Cover Photo: U.S. President Donald Trump (L) shakes hands with Russian President Vladimir Putin during a joint press conference at the Presidential Palace in Helsinki, Finland, July 16, 2018. /VCG Photo )