National Security Agency leaker Edward Snowden has applied for political asylum in Russia, Reuters and The Associated Press reported.
Earlier on Monday, Russian President Vladimir Putin said Snowden "must stop his work aimed at harming our American partners" if he wants to stay in the country.
Russian officials have said Snowden is in the transit area of Moscow's international airport.
A former computer security contractor, Snowden acknowledged in a Guardian newspaper interview last month that he leaked classified documents about U.S. surveillance of telephone and Internet traffic.
Snowden's disclosures have fueled new debate about the U.S. government's collection of records of domestic telephone calls and overseas Internet activity in the global hunt for terrorists and criminals.
Civil liberties advocates say the measures are unacceptable intrusions. But supporters say they are legal and have yielded evidence that has helped stop terror plots.