An American citizen has been arrested in Moscow on suspicion of espionage, Russia’s domestic security service, the FSB, said Monday. 

The agency identified the man as Paul Whelan. A criminal case has been opened against him. 

The U.S. State Department said it has been notified by the Russian Foreign Ministry of an American citizen’s detention but could not confirm the name or provide more details, citing privacy considerations. 

The United States has asked for consular access. “We have requested this access and expect Russian authorities to provide it,” a State Department spokesman said.

By Russian law, foreigners found guilty of spying on Russia face between 10 and 20 years in prison. 

“On December 28, staff members of the Russian Federal Security Service detained U.S. citizen Paul Whelan in Moscow while on a spy mission,” the FSB, the successor to the Soviet-era KGB service, said in a statement on its website. No other details were given. 

The arrest of the U.S. citizen comes as tensions between Washington and Moscow continue to escalate over a range of issues, including election interference and the crises in Syria and Ukraine. 

President Vladi­mir Putin, in his New Year’s greeting to President Trump, said he was open to a meeting of the two leaders. Trump canceled a formal meeting with Putin at the Group of 20 summit in Buenos Aires in December over Russia’s seizure of Ukrainian naval vessels and crew members. 

“Russia-U.S. relations are the most important factor behind ensuring strategic stability and international security,” Putin wrote to Trump on Sunday, in one of many messages to heads of state around the globe. 

The Foreign Ministry notified the U.S. Embassy in Moscow of Whelan’s arrest in compliance with procedure, the Interfax news agency cited officials there as saying. The ministry said his full name is Paul Nicholas Whelan, state-run media outlets reported. 

In December, Russian gun rights activist Maria Butina pleaded guilty to conspiring with a senior Russian official to infiltrate U.S. conservative groups. Butina, 30, is the first Russian national to be convicted of seeking to influence U.S. policy in the run-up to the 2016 election by acting as a foreign agent. 

Shortly before Butina pleaded guilty, Putin said she was not known to any of his spy agencies. The Foreign Ministry has gone to great lengths to paint Butina as a political prisoner, notably by launching a wide-ranging social media campaign.