Belgrade, Serbia-Montenegro ? The assassination of Serbia’s prime minister was orchestrated by a shadowy group that wanted to replace the pro-Western government with allies of Slobodan Milosevic, investigators said Tuesday.

The group behind Zoran Djindjic’s March 12 killing — called the “Hague Brotherhood” — hoped the assassination would create widespread chaos and planned to follow with a coup against Serbia’s government, the officials told The Associated Press on condition of anonymity.

But Djindjic’s Democratic Party quickly named a successor after his death and police cracked down hard, arresting 7,000 people, effectively spoiling the plan. The assassins also may have been caught off-guard by the huge public outpouring of grief over Djindjic’s death — nearly 1 million people attended his funeral.

Police believe a feared paramilitary group known as the Unit for Special Operations, formed during Milosevic’s rule, played a large role in the Hague Brotherhood. Its deputy commander, Zvezdan Jovanovic, was arrested soon after Djindjic’s slaying on suspicion of being the assassin.

Jovanovic told investigators he killed Djindjic because he was told his unit would be handed over to the U.N. war crimes tribunal in The Hague, Netherlands, the officials said.

At least four other plans to kill Djindjic failed on the eve of his slaying in downtown Belgrade, the officials said. One plan included firing anti-tank rockets at his armored car.

The investigation into Djindjic’s death led police to the body of another Milosevic foe, Serbian President Ivan Stambolic, who was slain in 2000. His death also has been blamed on Milosevic’s allies.

About 1,000 people attended Stambolic’s funeral Tuesday.

An arrest warrant was issued for Milosevic’s wife, Mirjana Markovic, in connection with Stambolic’s killing. Markovic, who fled the country for Russia weeks ago, denies involvement in his death.