After the assassination of pro-Western Prime Minister Zoran Djindjic earlier this month, many here feared that Serbia's reform efforts might stall.
But the politician's death appears to be having an opposite effect - propelling a campaign to root out corruption.
In their hunt for the assassins, police have rounded up thousands of suspected mafia figures in the biggest crackdown yet on organized crime in the Balkans.
"If they can keep this up for another two weeks, I am optimistic that Djindjic's death will be seen as the spark that gave Serbia a democratic future," says James Lyon, the representative of the International Crisis Group in Belgrade.
At the same time, however,many observers are warning that draconian emergency powers Serbian authorities imposed after Mr. Djindjic's murder could end up undermining Serbia's fragile democracy.
Police have filed nearly 400 criminal charges against underworld figures detained since Djindjic's March 12 death, Dragan Sutanovac, head of the Serbian parliament's Security and Defense Board, told independent B-92 radio Monday.
Serb police say their sweep through the underworld has confirmed that a Belgrade criminal ring known as the Zemun clan was behind Djindjic's murder. The gang has ties to the security apparatus of former Yugoslav President Slobodan Milosevic, whom Djindjic played a key role in overthrowing in October 2000.
Police have taken in more than 3,000 people for questioning and detained just over 1,000 of them. Not all the detainees will be prosecuted for involvement in the sniper attack on Djindjic, Sutanovac said, but for other criminal activities.
The arrested include key members of the Zemun gang, police say, but so far the three suspected ringleaders, including the alleged mastermind, a former commander of the Red Berets police special forces unit known as "Legija" (the Legionnaire), remain at large.
The dominant clan in the Belgrade underworld, the Zemun gang includes many former paramilitaries who fought for the nationalist Milosevic in the Balkan wars of Croatia, Bosnia, and Kosovo. After the conflicts, Milosevic gave them a free hand in drug trafficking, authorities say. Zemun crimes also include kidnapping, murder, and the smuggling of cigarettes, arms, and people.
The Serbian government has said Djindjic's murder was an effort by criminal overlords to sow chaos in Serbia.
As prime minister, Djindjic made many enemies. He angered nationalists by arranging Milosevic's arrest and extradition to the UN War Crimes Tribunal at the Hague, where he is now standing trial for crimes against humanity.
It is widely suspected that Djindjic made a deal with some elements of Milosevic's security forces under which they would not block the overthrow and he would not pursue them after the demo-cratic opposition took power.
The slain prime minister's foes have alleged that Djindjic had further ties with the paramilitaries-turned-mafia, including regular phone conversations with Legija, and participation in a cigarette-smuggling racket - an allegation Djindjic strongly denied.
Djindjic had pledged to clamp down on organized crime.
As the hunt for the assassins continues, some human rights groups warn that police and security officials are being granted the same kinds of powers they had under Milosevic. The state of emergency gives authorities extra latitude in making raids, and, under legislation left over from the Milosevic era, police can hold suspects for up to 30 days without charge or access to a lawyer.
The Belgrade office of Human Rights Watch (HRW) is calling for a delegation to determine if detainees are being beaten or tortured. HRW's Balkan researcher, Bogdan Ivanisevic, says that, although post-Milosevic authorities have not used police brutality against political opponents as strongman Milosevic did, such brutality has continued against prisoners in criminal cases.
"There have been dozens of cases recorded by reliable NGOs of beatings by the police, sometimes leading to deaths in custody," Ivanisevic says.
How long the emergency powers are in force is also a key question, he adds. "If the government continues the same level of control even when it is clear that there is no longer any threat to the life of the nation, there is more cause for concern."
Reporters Without Borders, an international media watchdog, has voiced concern over the government's use of the emergency powers to close newspapers and a television station critical of the authorities.
Officials say two of three newspapers banned in Serbia had links to the mob, and that the TV station was closed for showing pornographic movies during the three days of national mourning for Djindjic.
The dragnet has taken in several state security and police officials accused of corruption, including Serbia's deputy prosecutor, arrested for being on the Zemun clan's payroll.
• Material from wire services was used in this report.