The Russian intelligence service, the FSB, has begun a criminal investigation into alleged espionage connected to Britain's foreign intelligence service, MI6. The case is connected to the 'Litvinenko case'.

Charges are expected, following an FSB inquiry into claims by a Russian citizen that he's been working for MI6.

“The FSB has verified the claims of Mr Zharko about the circumstances of his co-operation with the British intelligence service. As a result, enough data was collected to indicate that during the period from 2003 to 2007, employees of MI6 had used him as an agent to conduct espionage activities. On the basis of this, a criminal case has been launched into intelligence gathering and subversive activities by British special services to the detriment of the external security of the Russian Federation,” said Sergey Ignatchenko, Head of Federal Security Service Public Relations Service.

Vyacheslav Zharko claims none of the work he did could be considered illegal by the Russian government as his reports to MI6 were taken from sources like the press and the Internet.

He came to the FSB earlier this year seeking protection over his communication with Aleksandr Litvinenko, a former Russian security officer murdered last November in London.

Vyacheslav Zharko said he had met with Litvinenko and exiled Russian businessman Boris Berezovsky numerous times.

In an interview with Russia Today, Mr Zharko claimed it was through Litvinenko that he became involved with MI6.

“Everything began in 2002. Aleksandr Litvinenko acquainted me with two officials from MI6, Secret Services as they called them. They suggested that I should provide them with some services on a compensatory basis,” Vyacheslav Zharko informed.

Zharko came forward with his claims following a press conference by one of the suspects in the Litvinenko case, Andrey Lugovoy.

During it, Mr Lugovoy had accused Britain of trying to recruit him for espionage.

He also said both Litvinenko and Berezovsky had been MI6 agents.

Britain had asked Russia for Andrey Lugovoy to be extradited to stand trial for Litvinenko's murder in London, a request Russia denied as the move was unconstitutional.

Though, Moscow hasn't ruled out the possibility of trying Mr Lugovoy on Russian soil, provided there is enough evidence from Britain.