Federal prosecutors alleged 11 people were spies living secret lives in American communities, from Seattle to Washington D.C., sent years ago to infiltrate U.S. society and glean its secrets.

In an extensive and bizarre affidavit whose details echoed Cold War spy thrillers, the Federal Bureau of Investigation claimed the alleged spies were sent here by the Russian overseas intelligence service known as the SVR—the successor to the Soviet KGB—as early as the mid-1990s, and were provided with training in language as well as the use of codes and ciphers.

Their mission, according to the FBI, was contained in an encrypted 2009 message from Russian handlers in Moscow to one of the defendants that read in part: "You were sent to USA for long-term service trip. Your education, bank accounts, car, house etc.—all these serve as one goal: fulfill your main mission, i.e. to search and develop ties in policy-making circles in U.S. and send Intels [intelligence reports] to" Moscow.

Many details of the alleged plot remained murky late Monday including the main impetus behind the intelligence program. The Russian embassy in Washington Monday said there wasn't anyone available to comment.

The U.S. and Russia have sent spies to each other's countries for decades, even in the 20 years since the Cold War ended. Still, the latest allegations come at a time when relations between the U.S. and Russia have been warming; last week, Russian President Dmitri Medvedev visited President Barack Obama in Washington.