The Russian security agency on Monday said that it has detained a US citizen in Moscow accused of spying. <br />''<br />''<br />''The FSB security service said in a statement that the American was detained on Friday while carrying out an act of espionage and that a criminal case had been opened. <br />''<br />''<br />''The statement identified the American as using a Russian name that appeared to translate as Paul Whelan. No other details have been released yet. <br />''<br />