The F.S.B., the successor to the Soviet-era K.G.B., identified the officer as Ryan Christopher Fogle and said he had been “working under the guise of” third secretary in the political department of the United States Embassy in Moscow. It said that Mr. Fogle was detained on Monday night and that he was carrying written instructions for a Russian recruit. Russia’s Foreign Ministry has summoned United States Ambassador Michael A. McFaul to appear on Wednesday to respond to the accusation. Photographs that appeared on Russian news sites on Tuesday afternoon showed a man in a blond wig, a blue checked shirt and a baseball cap being pinned to the ground, evidently by a Russian officer, and later sitting at a desk in an F.S.B. office, grim-faced. Further images showed a number of items evidently confiscated from him: brown and blond wigs, several pairs of dark glasses, several stacks of 500-euro notes, a compass, a map of Moscow and an embassy ID card identifying him as Ryan C. Fogle. Russian news sources also featured the text of a letter, allegedly addressed to a recruit, that instructs the recipient to create a Gmail account that will be used for covert contacts. The letter, signed “your friends,” offers $100,000 “to discuss your experience, expertise and cooperation,” with much greater rewards for answering “specific questions.” It goes on to say that “we can offer up to $1 million a year for long-term cooperation, with extra bonuses if we receive some helpful information.” Communications were to be addressed to an enigmatic e-mail address, unbacggdA@gmail.com. “This is a down payment from someone who is very impressed with your professionalism and who would greatly appreciate your cooperation in the future,” the letter says. “Your security means a lot to us. This is why we chose this way of contacting you.” Mr. Fogle was taken to F.S.B. headquarters and then delivered to officials at the American Embassy, the statement said. The F.S.B. went on to say its counterintelligence service has documented a series of recent attempts by the United States to recruit officers from Russian law enforcement and “special departments.” The United States Embassy has not commented on the report. The accusations come as Russian officials express high anxiety about what they describe as Western attempts to undermine political stability here. President Vladimir V. Putin has thrown his support behind new laws seeking to prevent Russian officials from keeping wealth overseas, saying it leaves them dangerously exposed to pressure from foreign governments. And nongovernmental organizations are being forced to brand themselves as “foreign agents” if they receive financing from other countries. Mr. Fogle’s arrest, lavishly detailed on Russian television, fell easily into that line of reasoning, though some of its details, like the pile of wigs, left many in Moscow incredulous. “There is nothing new about it — I’m just surprised that the guy was such an idiot,” said Yevgenia M. Albats, the author of a 1994 book on the K.G.B. “I am not interested so much in this Christopher Fogle as much as the person he was trying to recruit, and why did he have to do it in such an old-fashioned way? It sounds like the ‘70s.” In 2010, the American authorities arrested 10 people who were part of a Russian spy ring and had been living in the United States for a decade, posing as Americans. The so-called “sleeper” agents had not sent home any classified secrets and were not charged with espionage. Instead, they were sent back to Russia as part of a swap in which the Kremlin released four prisoners who had been jailed for spying, three of whom were serving long sentences. At the time, the Obama White House quickly made clear that it did not envision the episode causing undue strains with Russia. In recent days, President Obama and Mr. Putin have increased up cooperation on antiterrorism efforts in response to the bombing at the Boston Marathon. So it seemed likely that this latest espionage arrest would also not get in the way of larger bilateral priorities, including plans for the two presidents to meet in Ireland later this month and in Russia later this year. Since being expelled back to Russia, at least one member of the suburban spy ring, Anna Chapman, has become a celebrity here, with her own TV show. Espionage arrests, though not frequent, have long been an element of diplomatic life in Moscow. In May 2011, Russia expelled Israel’s military attaché in Moscow on suspicion of spying. The attaché, Vadim Leiderman, an air force colonel born in the Soviet Union, was arrested while sitting in a cafe with a Russian and was suspected of managing several local residents as informers. The Israeli Defense Ministry said it had conducted its own investigation and found the Russian accusations to be baseless. There have also been notable defections. In October 2000, Sergei Tretyakov, a colonel in the Russian spy service, defected to the United States with his wife and daughter. At the time, he held the title of first secretary of the Russian mission in New York and senior aide to the Russian ambassador to the United Nations, Sergey V. Lavrov. Mr. Lavrov is now Russia’s foreign minister.