Serbian police are conducting a wide-ranging manhunt for the killers of Prime Minister Zoran Djindjic, and have arrested several people linked to a crime syndicate, known as the Zemun gang, which the government says is behind Mr. Djindjic's assassination. The search for underworld figures comes as Serbs mourn the man many hoped would integrate their country into the European mainstream.
Police in Belgrade say that about 40 people directly or indirectly linked to the Zemun gang have been arrested so far, but that several prime suspects are still on the run.
The fugitives include Milorad Lukovic, a former police commander, ex-paramilitary leader and French Foreign Legion veteran, whom the government accuses of organizing the criminal network it says is to blame for Mr. Djindjic's assassination.
Mr. Djindjic, who was shot outside the main government building in Belgrade and later died of his wounds in a hospital, made many enemies by pushing for the arrest of mobsters and war crimes suspects.
The government has vowed to hunt down the killers and show them no mercy if they resist arrest.
As a state of emergency went into effect, top Serbian officials, foreign diplomats and members of the Djindjic family attended an official memorial service for the slain leader in Belgrade's city hall. Among those attending was Javier Solana, the European Union's foreign policy chief, who condemned the killing.
"A friend of mine has been killed," he said. "Zoran Djindjic was a very good friend. I had the opportunity of working with him. ... I had a very long conversation on the telephone the day before yesterday ... to help him make progress in the development of his country. I think this is a criminal act that has to be condemned by everybody."
Three days of official mourning for Mr. Djindjic are underway, and Serbian television reports he will be buried Saturday afternoon.
Meanwhile, diplomats at EU headquarters and at the NATO alliance in Brussels are expressing concern about Serbia's future in the wake of Mr. Djindjic's assassination.
They say Serbia needs to rapidly crush the criminal gangs that often operate with impunity in the country, or face chronic instability that could end up destroying its hopes of rejoining Europe.
The diplomats say the loss of the pragmatic, pro-Western Mr. Djindjic raises doubts about Serbia's ability to stay on the path of economic and political reform. Some EU officials fear his murder could paralyze foreign investment in Serbia, whose economy remains crippled after more than a decade of wars.
NATO officials say a break-up of Mr. Djindjic's fragile coalition could re-ignite Serbian nationalism and that, in turn, could have de-stabilizing effects, not only in Serbia but in neighboring Balkan areas, as well.