The death of former Russian spy, Alexander Litvinenko, last week from radioactive Polonium-210 poisoning is the latest in a series of politically motivated attacks on the outspoken opponents of Russian President Vladimir Putin.

No one has been able to officially implicate the Russian FSB - the domestic successor of the old Soviet KGB - in the assaults. But old-school KGB and CIA veterans are pointing fingers in the direction of the Kremlin and its supporters, the siloviki (powerful ones).

You can see why. For starters, "wet works" (i.e., politically motivated assassination by security services) originated in the early 20th century with the Soviet secret service, the NKVD. (The term comes from the notion that you'd get your hands "wet" with the victim's blood.)

And there is plenty of circumstantial evidence linking Russian spetzsluzhba (special services) in political "hits" using poison:

* In 2003, Yuri Shchekochkin, a journalist and Kremlin critic, died of an "allergic reaction" that was likely a deliberate poisoning.

* Journalist Anna Politkovskaya, a critic of Putin and the war in Chechnya, fell mysteriously ill while flying to negotiate the release of Beslan schoolchildren being held by Chechen terrorists in 2004. (She was ultimately gunned down in Moscow in October.)

* Also in 2004, pro-West Ukrainian presidential candidate Viktor Yushenko, running against pro-Kremlin candidate Viktor Yanukovich, was poisoned by suspected dioxins, making him ill and leaving his face severely disfigured.

And now Litvinenko - a KGB/FSB veteran whose investigations of corruption in Russia reportedly made a lot of enemies among his comrades, the siloviki and the Russian mafia - dies a painful death from ingesting a highly toxic radioactive isotope.

Litvinenko was likely a marked man. When the FSB fired him on Putin's orders, he fled into asylum to London's "Moscow on the Thames," becoming a fierce Putin/FSB critic. Most recently, he was investigating the Politkovskaya murder.

Russia's press (much of it now Kremlin-controlled) bristled at the suggestion of Putin's involvement in Litvinenko's death. The Kremlin has dismissed such talk as "sheer nonsense."

Sure, Putin is feeling pretty feisty these days; maybe he doesn't care what the world thinks of such brutality. Awash in oil/gas and playing a pivotal role in Iran's nuclear fate, Russian influence is anything but declining.

But neither the Kremlin nor the Russian intelligence services derive much benefit from such a risky, high-visibility assassination. Indeed, the potential diplomatic downsides in getting fingered for the killing would be significant.

While off-ing Litvinenko could deter other overseas Putin antagonists from speaking out, if the Kremlin were implicated in killing a regime opponent - a British citizen to boot! - in London, it would certainly put a frost on U.K.-Russian relations. Washington (already unhappy with Putin's de-democratization efforts and heavy-handed energy politics) would also have a hard time ignoring Moscow's murderous machinations.

And there's no telling how the European Union would react to Russian government involvement. The current Russia-E.U. Partnership and Cooperation Agreement is already in jeopardy, failing to come up for a vote just last week in Brussels.

And there's another obvious possible explanation. When former Russian President Boris Yeltsin disbanded the KGB, many newly unemployed operativniki (operatives) joined Russia's infamous organized crime world. Maybe the Russian Mafiosi didn't appreciate Litvinenko getting into their business - and decided to do something about it. Or perhaps they "did" him after the spetzsluzhba or siloviki put out a score-settling contract on him.

But that still doesn't answer the question of why the Mafiosi would use the dangerous-to-handle Polonium-210 instead of a simple bullet. That points back again to the Russian security services, known for being well schooled in the black art of poisons. So, while it seems quite plausible that Russian cloak and dagger killed Litvinenko, there are other scenarios, too. But if the Kremlin did order Litvinenko's assassination, it casts a frightening new light on the new Russia.