Russia on Tuesday said it had detained an alleged American CIA agent working undercover at the US embassy who was discovered with a large stash of money as he was trying to recruit a Russian intelligence officer.
Russia's Federal Security Service (FSB, ex-KGB) identified the man as Ryan C Fogle -- third secretary of the political section of Washington's embassy in Moscow -- and said he had been handed back to the embassy after his detention.
In the latest espionage scandal that risks rocking US-Russia relations at a sensitive time, the Russian foreign ministry said it was summoning US ambassador Michael McFaul on Wednesday to provide an explanation.
Photographs published by state English language television RT showed Fogle being held to the ground face down and having his hands put behind his back for the arrest.
He was then shown being questioned at the Federal Security Service while documents such as his passport and a stack of 500 euro notes along with some letters were displayed.
Pictures were also shown of his alleged espionage equipment including wigs, a compass, torch and even a mundane atlas of Moscow as well as a somewhat old fashioned mobile phone.
The FSB said in statement carried by Russian news agencies that Fogle was carrying "special technical equipment, written instructions for recruiting a Russian citizen, a large sum of money and means for changing a person's appearance."
The statement added that "recently, the US intelligence service has made repeated attempts to recruit the staff of Russian law enforcement agencies and special services, which were detected and carried out under control of the Russian FSB counter-intelligence service."
The Russian news agency reports said the suspected agent had been caught red-handed trying to recruit an employee of one of the Russian security services.
It is not clear what will now happen to Fogle but normal practice in Russia would be for him to be declared persona non grata and ordered to leave within 48 hours or less.
The incident comes amid a new chill in Russian-US relations sparked by the Syrian crisis and concern in Washington over what it sees as President Vladimir Putin's crackdown on human rights.
The last major spy row between the two former Cold War rivals involved the glamourous Anna Chapman and 10 other Russian spies arrested in the US in 2010.
The spy scandal -- which ended with a swap of the 10 sleepers and four Russians convicted of spying for the West -- was a huge embarrassment for Russia's foreign intelligence at the time.
Several of the spies were portrayed by the press as bumbling amateurs who had accomplished little through careers that in some cases stretched back to the Soviet era.
On Tuesday, the FSB and Russia's tightly-controlled state media appeared intent on showing to the public that the man it had caught was a real agent who posed a danger to Russia's interests.
The photos published by RT also showed a document entitled "printed instructions for the Russian citizen being recruited".
Parts of the recruiting document allegedly used by Fogle read: "Dear Friend. This is an advance from somebody who is impressed with your professionalism, and who would value highly your future cooperation with us."
The document added that the US government was willing to pay $100,000 outright.
"Payment can be much higher if you are ready to answer specific questions," it added.
"Besides, we offer up to $1 million per year for long-term cooperation, with a promise for an additional bonus for information that will help us."
McFaul -- who was doing a question-and-answer session with Russians on his Twitter account at the time the news broke -- tweeted "No" when asked if he could comment on the incident.