Litvinenko, an outspoken critic of President Vladimir Putin's administration and a close associate of fugitive oligarch Boris Berezovsky, died in a London hospital November 23. His body was found to contain a lethal dose of polonium-210, a radioactive isotope.
Moscow officially joined the investigation Thursday, with the country's top prosecutors filing criminal cases into his death, and a related murder attempt on Russian businessman Dmitry Kovtun, currently in hospital.
Kovtun, who met with Litvinenko in London in October, was diagnosed with an illness also caused by radiation poisoning.
Media reports cited an unidentified source as saying Kovtun was had been admitted to hospital in a critical condition Thursday evening, after being questioned by Russian and Scotland Yard investigators; however, a lawyer close to the case denied the reports.
Andrei Romashov, a lawyer for Andrei Lugovoi, Kovtun's business partner, called the reports a "provocation".
The Prosecutor General's Office said criminal cases had been launched following the post mortem and forensic examination of Litvinenko's body.
Russian-British investigation
British police said Wednesday that they will investigate Litvinenko's case as a murder, in view of the preliminary results of the forensic examination. They arrived in Moscow Monday to interview people who had met with Litvinenko, a British national, around the time of his reported poisoning at the beginning of November.
Andrei Lugovoi, a businessmen and former officer of the Federal Protection Service, who served as a bodyguard for Boris Berezovsky, was expected to be questioned Thursday.
However, the questioning was postponed for "technical reasons," his defense lawyer said, citing Russian law enforcement officials, who gave no more details for their decision.
Lugovoi told The Times and The Daily Telegraph last week that he and two of his business partners had met with Litvinenko in London November 1, the day he is believed to have received a fatal dose of Po-210.
Traces of radiation have been detected in the hotel rooms in London where Lugovoi stayed in October and November, and on the airliners in which he flew to the UK, the popular Russian daily Kommersant said Wednesday.
Scotland Yard detectives are also unlikely to interview Litvinenko's jailed fellow security officer Mikhail Trepashkin, who was found guilty in 2004 of divulging state secrets, and is currently serving a four-year sentence.
Trepashkin earlier said in a letter that he had warned Litvinenko of a planned attempt on his life to avenge his defection in 2000. His defense lawyer said Monday he is prepared to give evidence in the case to the British security services.
But the Russian prison service ruled out Wednesday the possibility of British detectives meeting with Trepashkin, saying a person sentenced for treason cannot contact foreign security services.
The Russian Prosecutor General's Office said its experts may fly to Britain "for a complete and comprehensive investigation of this criminal case."
Polonium-210 origin and traces
In the course of Scotland Yard-led investigations into Litvinenko's poisoning, radiation has been found at a dozen sites in the UK and on two British Airways aircraft that flew the London-Moscow route. British experts also found insignificant traces of radiation in the U.K.'s Moscow Embassy.
Seven staff working at a bar in the Millennium Hotel visited by Litvinenko on the day he fell ill, also have tested positive for low levels of Po-210, Britain's Health Protection Agency said Thursday.
Moscow has flatly denied that the Po-210 used to kill Litvinenko could have come from Russia.
Five Russian companies and the chemistry faculty of Moscow State University hold licenses to deal with substances containing polonium-210, the national nuclear watchdog said Thursday.
Enterprises at the Federal Nuclear Center in the Volga city of Samara hold three licenses to handle Po-210, a uranium by-product, and two others are owned by Techsnabexport, the state-controlled uranium supplier and provider of uranium enrichment services, as well as one private company, Nuclon.
According to Nuclon's Web site, the company supplies medical preparations and radioactive and stable isotopes, and provides transportation services.
Konstantin Pulikovsky, the head of the Federal Service for the Oversight of the Environment, Technology and Nuclear Management, said earlier that no nuclear materials storage or transportation violations had been revealed during checks at enterprises that the agency monitors.
"When the subject began to be discussed in the press, we carried out additional checks everywhere. I can say with complete certainty that no deviations from the rules on storage and transportation of nuclear materials, including polonium, have been discovered at any structures of our fuel and nuclear complex," he said.
Russian intelligence veterans and Kremlin enemies under the spotlight
A Russian intelligence services veterans association dismissed allegations of its involvement in Litvinenko's death.
There have been reports in Western media suggesting that Honor and Dignity, a foundation of veterans of Russia's intelligence and diplomatic services, might have been involved in the murder.
A foundation spokesman speaking on the condition of anonymity dismissed assertions that foundation president Valentin Velichko, a former Federal Security Service (FSB) officer, may have played a part in Litvinenko's murder.
"This is groundless, unsubstantiated information," he said, adding the group considering a lawsuit against the media outlets that made these allegations.
A former acting prime minister said Thursday that enemies of Russia may have been involved in the poisoning of Litvinenko, and dismissed the possibility of state involvement.
Yegor Gaidar, 50, an architect of economic reforms in post-Soviet Russia, began vomiting and bleeding from the nose before fainting at a conference in Dublin November 24.
Although he was discharged from a Moscow hospital, Russian doctors were unable to identify the exact cause of his illness.
In an interview with the Vedomosti business daily, he said that if it was an attempt on his life, it could only have been related to politics.
"Who in Russia would stand to gain from my death on November 24, 2006 in Dublin? After some consideration, I immediately dismissed the theory that the Russian leadership might have been involved in what happened. After Alexander Litvinenko's death, yet another murder of a well-known Russian the following day was the last thing Russia's ruling authorities would have been interested in," he said.
Diplomatic impact
Russian Foreign Minister Sergei Lavrov said Thursday investigations into the murder would not affect Russia's approach to relations with Britain.
Litvinenko's case has strained tensions between London and Moscow. Before his death, the Russian defector reportedly accused the Kremlin and the president of ordering his murder in a deathbed note dictated to an acquaintance, a charge that Moscow dismisses.
"I cannot judge how this is affecting [relations] on the British side," Sergei Lavrov said, adding that attempts to make a political sensation out of the case are futile. "We have always been ready to assist the investigation."
British Ambassador in Moscow Tony Brenton, speaking on the high-pitched media coverage of the case, said earlier this week that papers could write whatever they liked, but that the British government does not view the investigation into Litvinenko's death as part of an anti-Russian campaign.
The poisoning has triggered a heated media debate and parallels to other high-profile assassinations in Russia recently, in particular the murder of another outspoken critic of the Kremlin, journalist Anna Politkovskaya, in October.
On Monday, Lavrov condemned attempts to fan the scandal and admitted the affair could damage Russian-British relations.
Litvinenko's funeral
Four cars with tinted windows drove to north London's Highgate Cemetery, cordoned off by police, at about 1 p.m. GMT, with several dozen reporters already waiting at the gates.
Relatives and friends, including Boris Berezovsky, wanted in Russia for fraud, and Chechen militant Akhmed Zakayev, wanted by Moscow for acts of terrorism, came to pay their last respects to Litvinenko, who according to his father converted to Islam soon before his death.
Highgate Cemetery is a famous graveyard opened in 1839 as one of seven large cemeteries, known as Magnificent Seven, around London. The cemetery is the final resting place for many historical figures, among them German philosopher and revolutionary Karl Marx, novelist George Elliot, and scientist Michael Faraday.
Western media reported earlier that Litvinenko's body would have to be sealed in an airtight container due to radioactivity risks, and that he cannot be cremated for 22 years.
