Moscow, Russia (CNN) -- The British journalist expelled from Russia was denied entry when he came back to the country because "he violated a number of rules concerning the work of foreign correspondents," the Russian Foreign Ministry said on its website Tuesday.
Luke Harding, the Moscow reporter for the Guardian newspaper, 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. He had been returning to Moscow after spending two months in London reporting on the U.S. diplomatic cables published by the website WikiLeaks.
The British Foreign Office said the incident occurred on Saturday.
Alan Rusbridger, the Guardian's editor, said in a statement that Russia's move was "a very troubling development with serious implications for press freedom."
But the Russian Foreign Ministry statement said the rules allegedly violated were set down in 1994 and are "well known" to all working journalists in the country.
"In particular, having applied for and received the extension of his accreditation at the end of November last year, Harding left Moscow for London for his own business without receiving a (new) foreign correspondent press card issued in his name, although he knew he should have done that.
"Therefore, if L. Harding is still interested in working in Russia during the validity term of his Russia visa, he needs to settle the issues related to his accreditation with the Russian Foreign Ministry Information and Press Department.
"If L. Harding complies with these rules, which are the same for all foreign correspondents, there will be no problems with his entry to the Russian Federation," the statement said.
In a statement to Parliament, Britain's Minister for Europe David Lidington made reference to the accreditation issue but not specifically the foreign correspondent press card.
"Indeed, last November the Guardian approached us for support to secure Mr. Harding's reaccreditation as a journalist when his accreditation had been withdrawn. We made representations at a senior level and in the event, Mr. Harding was granted an extension of his accreditation as a journalist."
Lidington said Harding had not been "given any explanation for his exclusion" and deplored any restrictions on free media and freedom of expression.
"We understand that Mr. Harding had previously been warned by the Russian authorities about several alleged violations of his status as a journalist -- including visits without permission to border zones and classified areas," he said.
Lidington said Harding "knows Russia well and has, over the last four years, given readers of the Guardian genuine insight into that country."
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.
CNN's Maxim Tkachenko contributed to this report