By Gabriel Partos
BBC South-East Europe analyst
A statement by the Serbian Government puts the blame for Prime Minister Zoran Djindjic's assassination on one of the organised crime groups that emerged during the long rule of the former authoritarian leader, Slobodan Milosevic.
The statement names 20 members of the so-called Zemun group - named after a suburb of Belgrade - which is allegedly led by Milorad Lukovic, a former commander of a special police force unit, known as the Red Berets.
Mr Lukovic, nicknamed Legija because he was once a soldier in the Foreign Legion, played an instrumental part in the downfall of Mr Milosevic.
Djindjic was said to be planning a crackdown on organised crime
When huge crowds marched through the streets of Belgrade in October 2000 to demand that Mr Milosevic hand over power after his defeat in the presidential elections, Legija and other senior officers ensured that the security forces did not crack down on the demonstrators.
But subsequently Legija fell out with the new post-Milosevic authorities and he was sacked.
It was after that rift that he allegedly took over as head of the Zemun group which has been fighting for supremacy in Belgrade's criminal world with its main rivals the Surcin group - named after another suburb.
According to the Serbian Government's statement, it was Mr Djindjic's determination to crack down on organised crime that sealed his fate.
The new authorities have at times turned a blind eye to the mafia bosses - particularly when these individuals began to turn their criminal enterprises into more like legitimate businesses
The Belgrade authorities say that a fresh concerted attempt was to be made against the Zemun group which, according to official figures, has some 200 members. The government says it was to forestall this attempt that the murderers struck.
Earlier evidence that this may have been the case came last month when an apparent attempt was made on Mr Djindjic's life.
A lorry driven by another alleged member of the Zemun group, Dejan Milenkovic - nicknamed Bugsy - apparently tried to ram the prime minister's car which was in the middle of an official convoy.
Mr Djindjic said that such attempts would not succeed in diverting Serbia from the path of reform.
Curiously, though, the investigative judge released "Bugsy" from detention, and the alleged perpetrator has since disappeared.
But the argument that Mr Djindjic had to die because of his determination to deal with organised crime is not as clear cut as it appears.
Mr Djindjic inherited a burdensome legacy from Mr Milosevic, one of whose hallmarks was the close relationship - even intermingling - between the worlds of business, organised crime and the security forces.
Djindjic also made enemies for his role in Milosevic's arrest
Even if Mr Djindjic had been willing or able to crack down on the criminal elements from the very beginning of his term in office, he could have upset the balance of the barely functioning of the Serb economy.
Instead, the new authorities have at times turned a blind eye to the mafia bosses - particularly when these individuals began to turn their criminal enterprises into more like legitimate businesses.
Legija and his associates may have felt that they were being bypassed and that others, such as the alleged head of the rival Surcin group, Ljubisa "Cume" Buha were being favoured.
It seems that the most likely reason for Mr Djindjic's assassination was, indeed, organised crime - and the fears of mafia leaders that they might face an onslaught from the forces of law and order.
But Mr Djindjic had made many enemies - not least among the former Milosevic establishment because he had transferred Mr Milosevic to the Hague tribunal to face charges of war crimes.
Others in the ex-army circles involved in the protection of the wartime commander of Bosnian Serb forces, General Ratko Mladic, may have thought that the Belgrade authorities might try to arrest Mr Mladic and send him to The Hague.
It is possible that the continuing links between organised crime and former members of the security forces may provide the key to solving the murder of Mr Djindjic. It will not be an easy investigation.