[JURIST] Russia expelled four British diplomats [MFA press release] and suspended counter-terrorism cooperation with the UK Thursday in response to Monday's expulsion of four Russian diplomats [JURIST report] from the UK in protest over Russia's refusal to extradite Russian citizen Andrei Lugovoy [JURIST news archive] for the poisoning-murder of former KGB agent Alexander Litvinenko [BBC profile; BBC timeline] in London last year. The UK expressed disappointment in the Russian expulsions, and called them "completely unjustified" [FCO press release].
Russia has repeatedly refused UK requests to extradite Lugovoy, saying that to do so would violate the Russian constitution [MFA statement; JURIST report]. On Wednesday, the UK formally rejected [JURIST report] a Russian proposal to try Lugovoy in Russia, contingent on the UK presenting evidence of guilt. AP has more.