A former KGB agent struggling with a near-fatal dose of nerve poison in a London hospital may or may not be the latest in a long line of Kremlin foes to meet a harsh fate.
But the alleged poisoning of Alexander Litvinenko, who turned against the FSB security service and fled to Britain to join forces with exiled oligarch Boris Berezovsky, has been greeted with the same Kremlin stonewall and blackout in the state-run media as have similar cases in the past.
"The Litvinenko poisoning is simply not a story on Russian state TV, which reaches 100-million people, because politics in this country is 100 per cent controlled by the Kremlin," says Masha Lipman, an expert with the Carnegie Centre in Moscow. "A few Moscow newspapers have covered the story, but this reaches a very small audience."
In 2002, Litvinenko provided "evidence" included in a Berezovsky-produced film that claimed the Kremlin was behind a series of terrorist apartment bombings in 1999 that killed 300 people. In the wave of public panic that followed the bombings, former KGB agent Vladimir Putin swept to power promising to fight terrorism and restore order.
The film, which infuriated the Kremlin, was never shown in Russia but was widely screened in the West.
Russian security forces officially claim they have never "eliminated" an opponent on foreign soil since the 1959 murder of Ukrainian nationalist leader Stepan Bandera in Munich. The Kremlin has dismissed claims of FSB involvement in Litvinenko's poisoning as "sheer nonsense".
But a long string of unexplained killings or attempted murders often using poison of political opponents of the Kremlin since Putin came to power 6 years ago has given critics grounds to argue that the truth may be more complicated:
* In 2002 a Saudi-born Chechen rebel leader, Omar ibn Khattab, died after receiving a letter with poisoned ink. The FSB never claimed credit, but was widely assumed to be the letter's author.
* In 2003 a leading Russian journalist and anti-Kremlin parliamentarian, Yury Shchekochikhin, died of what appeared to be poisoning. His friends accused the FSB of involvement
* In 2004 a former president of the separatist Chechen republic, Zelimkhan Yandarbiyev, was killed by a car bomb in Qatar. Two Russian FSB agents were arrested and convicted in Qatar, but later released under strong diplomatic pressure from Russia.
* Also in 2004 pro-Western Ukrainian presidential candidate Viktor Yushchenko was hospitalized with dioxin poisoning, which disfigured his face and nearly killed him. Though the culprits have never been caught, Ukrainian experts believe the FSB may have carried out the poisoning to help pro-Russian candidate Viktor Yanukovych get elected.
* In September, investigative journalist Anna Politkovskaya was gunned down at the entrance to her apartment building in Moscow. A fierce critic of the Kremlin, Politkovskaya had earlier accused the FSB of trying to poison her during a flight to Beslan in 2004.
"In all of these cases, it's impossible to know the truth," says Lipman. "But critics will persist in fearing Kremlin involvement because, frankly, that's what has happened so often in Russian history."