The announcement in Qatar that two Russian intelligence agents have been charged with involvement in the assassination of former Chechen leader Zelimkhan Yanderbiyev has sparked official outrage in Moscow.
By Sarah Rainsford
BBC News, Moscow
Ivanov says the agents were in Qatar on legitimate business
Russia's acting Foreign Minister, Igor Ivanov, has been broadcasting repeatedly on state-run television condemning the arrests as an act of provocation.
According to Mr Ivanov, the agents are innocent. He claims they were in Qatar on legitimate business, gathering information for the international fight against terrorism.
But the suspicion that Russia's intelligence agencies may be behind the killing is not new. The one-time separatist leader of Chechnya was one of Moscow's most wanted men.
Zelimkhan Yanderbiyev was targeted by a powerful car-bomb as he drove home from Friday prayers in Doha on 13 February.
Just hours later - as the former rebel president lay fighting for his life - Russia's foreign intelligence body was already denying all responsibility.
Spokesman General Boris Labusov insisted the SVR had not assassinated anybody abroad since 1959.
So if not Moscow, then who?
The FSB, successor agency to the KGB, was quick to offer alternative explanations.
Former spy chief Nikolai Kovalyov suggested Mr Yanderbiyev had been killed by fellow Chechens, in revenge.
"Taking national traditions into consideration, I'm inclined to believe this was the result of a blood feud," Mr Kovalyov told Russian media at the time.
"A huge amount of blood has been spilled in Chechnya, and that is never forgotten."
Then another suggestion surfaced: that Mr Yanderbiyev had falled victim to a deadly dispute over funding.
Moscow believes Zelimkhan Yanderbiyev was a link-man in Doha between rebel militants in Chechnya and their sponsors abroad. They accuse him of channelling cash for terrorists.
The suggestion that someone was angry at missing out on their fair share was initially attributed to "security sources". It soon became Russia's chief official theory.
But the news that the authorities in Qatar have charged two Russians in connection with the killing has rekindled initial suspicions.
Protesting too much?
Igor Ivanov may be furious, but is his official protest entirely convincing? Many here believe Moscow had all the motive it needed.
Zelimkhan Yanderbiyev died just a week after the Moscow metro bomb: a powerful blast that killed and maimed dozens of commuters.
President Putin blamed the attack on Chechen rebels. He urged law enforcers to step up their fight against terror.
The angry statement from the Foreign Ministry refers to Zelimkhan Yanderbiyev as one of the most dangerous terrorists around.
Russia had been seeking Mr Yanderbiyev's extradition
Moscow had long been pushing for his extradition - but Doha refused to comply.
Russia links Yanderbiyev to the invasion of Dagestan in 1999 by Chechen rebels. More recently still, security sources claim he received calls from armed rebels as they held hundreds hostage in a Moscow theatre.
But the former rebel leader remained beyond Russia's reach, even after his inclusion on a UN list of people with suspected links to al-Qaeda.
Gennady Dudkov - a former spy turned MP - criticised the arrests in Qatar as a violation of international practice.
He told Russian radio that Doha has no proof Moscow was in any way involved in Mr Yanderbiyev's death.
Mr Gudkov claimed the secret unit that once conducted assassinations was disbanded long ago.
Some people here are no longer so sure.