Britain says it is extremely disappointed at Russia's refusal to extradite Britain's prime suspect in the murder of former Russian spy, Alexander Litvinenko.

Prime Minister Gordon Brown's office made the comment Tuesday, after British prosecutors said they had received Russia's formal letter of refusal to extradite Andrei Lugovoi.

The director of public prosecutions, Ken MacDonald, confirmed that Russia had offered to try Lugovoi, but insisted that London was the "appropriate" venue for hearing the case.

Britain alleges that Lugovoi murdered Litvinenko - who had become a British citizen - in London by deliberate poisoning him with radioactive polonium-210 last November.

Some information for this report was provided by AFP, AP and Reuters.