BELGRADE, Serbia-Montenegro — Anti-terrorist police moved Friday to demolish the sprawling headquarters of an underworld group linked to Slobodan Milosevic, as authorities accused allies of the former president of assassinating Serbia's prime minister.

Two bulldozers crushed concrete walls and smashed windows after masked policemen in bulletproof vests and toting machine-guns raided a shopping mall that was part of about a dozen edifices belonging to the shadowy gangland Zemun Clan, named after a Belgrade suburb.

The sprawling compound, owned by one of the group's ringleaders, Dusan Spasojevic, appeared empty.

The government has accused the underworld clan and other Milosevic allies of organizing and carrying out the murder of Prime Minister Zoran Djindjic on Wednesday in a sniper ambush.

The government said in a statement that the police investigation showed that the "criminal clan, as well as some other groups, mainly police-security structures from Milosevic's times," were behind the assassination.

During Milosevic's regime, underworld figures, war criminals and war profiteers formed close ties. Authorities said they had now joined forces to prevent Djindjic's efforts to battle crime and bring war crimes suspects to justice.

By Thursday afternoon, 56 suspects had been arrested. Police said several more individuals were apprehended Friday in a police sweep, dubbed Operation Whirlwind.

The police said they were using "all available police and technical resources" in the manhunt for Djindjic's assassins and were assisted by police of "practically all European countries."

But the Zemun Clan chiefs - among them Milorad Lukovic, nicknamed Legija - remained at large and authorities appealed to the public for information on their whereabouts.

Of those already arrested, eight were members of the group's inner circle. Three of them have offered to testify against others in exchange for police protection, the government said.

Djindjic, 50, was instrumental in ousting Milosevic and extraditing him to the UN war crimes tribunal in The Hague. That, along with his pro-western stance and his recent declaration of an open war against organized crime and corruption, made him many enemies.

Serbian authorities introduced a nationwide state of emergency following Djindjic's death. It allows police and the military to arrest suspects without warrants and detain them for up to 30 days without charges.

Preparations were underway for Djindjic's funeral, scheduled for Saturday. After lying in state and a mass at the main Orthodox Christian Temple, his coffin will be carried in a procession to Belgrade's cemetery for a burial with top honours.

Several foreign dignitaries announced they would attend the funeral, among them Britain's Robin Cook, Italy's Romano Prodi and Austrian Chancellor Wolfgang Schuessel. Chief UN war crimes prosecutor Carla Del Ponte was also expected.

"Serbia cannot make up for this loss," Deputy Prime Minister Zarko Korac said at a government commemoration ceremony Friday. "Courage was the basic characteristic of our late prime minister, and that courage changed Serbia."

In the Zemun suburb, many local residents applauded as police demolished the underworld headquarters.

"This should have been done long ago," said Teodora Aleksic, 21, a student from the neighbourhood. "Everyone knew they were criminals, those people living there. They built this with blood money."