Ryan Fogle, a third secretary at the U.S. Embassy in Moscow, was carrying special technical equipment, disguises, written instructions and a large sum of money when he was detained late Monday, Russia's Federal Security Service said.
The FSB, which is the successor to the Soviet-era KGB, said Fogle was trying to recruit a Russian counterterrorism officer who specializes in the Caucasus, a region in southern Russia that includes Chechnya and Dagestan. The suspects in the Boston Marathon bombings are ethnic Chechen brothers and the elder brother spent six months last year in Dagestan, now the center of an Islamic insurgency.
U.S. investigators have been working with the Russians to try to determine whether Tamerlan Tsarnaev had established any contacts with the militants operating in Dagestan.
Fogle, who was handed back to U.S. Embassy officials, was declared persona non grata and ordered to leave Russia immediately, the Foreign Ministry said. He has diplomatic immunity, which protects him from arrest.
It was the first case of an American diplomat publicly accused of spying in about a decade and seemed certain to aggravate already strained relations between Russia and the U.S.
The Foreign Ministry summoned Ambassador Michael McFaul to appear Wednesday in connection with the case. McFaul, who was doing a question-and-answer session on Twitter when the detention was first announced, said he would not comment on the spying allegation.
Noting recent efforts by the two countries to improve cooperation in countering international terrorism in the wake of the Boston bombings, the Foreign Ministry said "such provocative actions in the spirit of the Cold War do nothing to strengthen mutual trust."
Despite the end of the Cold War, Russia and the United States still maintain active espionage operations against each other. Last year, several Russians were convicted in separate cases of spying for the U.S. and sentenced to lengthy prison sentences.
Russian state television showed pictures of a man said to be Fogle, wearing a baseball cap and what appeared to be a blond wig, lying face down on the ground. The man, now without the wig, was also shown sitting at a desk in the offices of the FSB. Two wigs, a compass, a map of Moscow, a pocket knife, three pair of sunglasses and packages of 500 euro notes were among the items displayed on a table.
Russian state television also displayed a typewritten letter it described as instructions to the Russian agent who was the target of the alleged recruitment effort. The letter, written in Russian and addressed "Dear friend," offers $100,000 to "discuss your experience, expertise and cooperation" and up to $1 million a year for long-term cooperation. The letter also includes instructions for opening a Gmail account to be used for communication and an address to write. It is signed "Your friends."
In Washington, the White House referred questions about the detained diplomat to the State Department. There was no immediate response from the State Department. The CIA declined to comment on the case.
Little was immediately known about Fogle. A third secretary is an entry level position in the State Department, the lowest diplomatic rank in the foreign service.
President Vladimir Putin has stoked anti-American sentiments among Russians in recent years in what is seen as an effort to bolster his support at home. He also appears to have a genuine distrust of Russian nongovernmental organizations with American funding, which he has accused of being fronts that allow the U.S. government to meddle in Russia's political affairs. Hundreds of NGOs have been searched this year as part of an ongoing crackdown.
Mark Galeotti, a professor at New York University who studies the Russian security services, said the public exposure of Fogle and the pictures splashed across Russian television suggest a political purpose behind the detention. He said these kinds of spying incidents happen with some frequency but making such a big deal of it is rare.
"More often, the etiquette is that these things get dealt with quite quietly - unless they want to get a message out," Galeotti said. "If you identify an embassy staffer who is a spy for the other side, your natural impulse is to leave them be, because once you identify you can keep tabs on them, see who they talk to, and everything else. There's no reason to make a song and dance, detain them, eject them."
Russia and the United States have been at odds lately over Syria, the adoption of Russian children and U.S. sanctions against Russian officials accused of human rights abuses.
Galeotti, however, said the Fogle case was unlikely to affect the recent increased cooperation between U.S. and Russian counterintelligence agencies over the Boston Marathon bombings.
"Everyone goes into intelligence sharing knowing there's a parallel process where everyone spies on everyone else," he said.
Associated Press writer Max Seddon contributed to this report.