The free speech association "Anna Politkovskaya" claims there are parallels between the assassination of Bulgarian dissident writer Georgi Markov and those of Anna Politkovskaya and Alexander Litvinenko, media reports said.
The association has turned to Bulgaria's Chief Prosecutor Boris Velchev insisting he urged the UK government's emergencies committee, known as Cobra, to resume the investigation into the assassination of Georgi Markov.
Cobra was set up to investigate Litvinenko's death immediately after it was discovered he was poisoned with the radioactive element polonium-210. (As well as in his body, traces of the element were found in Mr. Litvinenko's home and in two restaurants he visited before falling ill).
Georgi Markov was murdered in London in 1978 when poison was secretly injected into his leg through the tip of an umbrella. No one has been charged with the killing, and in 2000 Bulgaria officially closed the case. The day was Bulgaria's communist dictator Todor Zhivkov's birthday.
Alexander Litvinenko was assassinated after he took part in the independent investigation of Anna Politkovskaya death. And she was murdered on Vladimir Putin's birthday, representatives of the association said.