The U.S. Embassy in Moscow had no immediate comment.
Russian officials have arrested a US citizen supposedly caught in the act of spying in Moscow, the Federal Security Service of Russia said Monday.
The FSB said the American was detained "during a spying action" on December 28 and that an investigation had been opened against him. Such an offence carries a prison sentence of up to 20 years.
Shortly before her guilty plea, Russian President Vladimir Putin said Butina was not known to any of his spy agencies.
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De Leon also told KNX-AM radio in Los Angeles that the sheriff was politicizing a tragedy and actually harming police work. Trump's demand that Congress approve $5 billion for a US southern border wall has led to a partial government shutdown.
"We are deeply concerned for his safety and well-being. His innocence is undoubted and we trust that his rights will be respected", the statement ended.
Paul Whelan is director of global security for Michigan-based automotive components supplier BorgWarner, the company said Tuesday. Whelan's brother David Whelan released a statement on behalf of the family, saying that Paul, who served multiple tours in Iraq, was in Moscow to attend a wedding.
A spokeswoman for Kelly Services told DailyMail.com that a Paul Whelan was employed there until February 2016.
Public accusations of spying have become more commonplace in recent years, as relations between the United States, the United Kingdom, and Russia have deteriorated since the Russian invasion of Crimea in 2014.
This is a developing story, check back for updates.