British reporter expelled from Russia

Moscow, Russia (CNN) -- The Guardian newspaper in Britain says its Moscow reporter, Luke Harding, has been expelled from Russia.

There's been no formal explanation given by the Russian authorities.

Alan Rusbridger, the Guardian's editor, said in a statement that the move was "a very troubling development with serious implications for press freedom."

Harding had been returning to Moscow after spending two months in London reporting on the U.S. diplomatic cables published by the website WikiLeaks.

On arrival, he was detained by Russian authorities, locked in a cell for 45 minutes, and then put on a plane back to London, according to an article in the Guardian Tuesday.

Assigned to Moscow since 2007, Harding covered many events, including the 2008 war between Russia and Georgia and the twin suicide attacks on the Moscow metro system in 2010.

He also wrote a number of controversial articles, including one on the speculation surrounding the alleged secret wealth of Russia's powerful prime minister, Vladimir Putin.

Last year, Harding was reprimanded by Russian authorities for unauthorized travel to areas closed to journalists.

"It is worrying that the Russian government should now kick out reporters of whom they disapprove. Russia's treatment of journalists -- both domestic and foreign -- is a cause of great concern," Rusbridger said.