British newspaper The Independent said Wednesday that Italian security expert Mario Scaramella, who met with Litvinenko shortly before his death, confessed that Litvinenko had told him about his involvement in an operation to bring a batch of smuggled radioactive materials to Zurich in 2000.
"It is no big secret that we are investigating several attempts to smuggle radioactive materials together with our American and European partners," Anatoly Safonov, the presidential representative for international cooperation on combating terrorism and organized crime, said.
However, these investigations were under way long before the recent scandal over Litvinenko's alleged poisoning, he said.
Safonov denied Russian special services' involvement in radioactive smuggling.
Safonov also said Russia and the UK will cooperate in investigating the ex-spy's death.
Litvinenko, a Russian intelligence defector, died November 23 in a London hospital with symptoms of radioactive poisoning. British health officials said Friday a large dose of polonium-210, a toxic uranium by-product, had been found in his body.
British Airways announced Wednesday that radiation had been found on two of their planes that traveled the Moscow-London route, as part of investigations into the case, and have been grounded at London's Heathrow Airport. Traces of radioactive contamination were also found on board a third BA plane in Moscow's Domodedovo Airport Thursday.
After Litvinenko died, the Western press circulated message purporting to be his deathbed note, in which he accused President Vladimir Putin of orchestrating his death, an allegation that the president dismissed.
The post-mortem and forensic examination of Litvinenko's body has been scheduled for December 1.
Scotland Yard investigators have discovered traces of Po-210 at six locations in the British capital that Litvinenko visited at around the time of his alleged poisoning at the beginning of November.