Serbian authorities say more than 1,000 people have been arrested in connection with the assassination of Prime Minister Zoran Djindjic.
The Serbian authorities are in the midst of a massive crackdown
The government also says Serbia's deputy prosecutor, Milan Saraljic - who was arrested on Wednesday - has confessed to links with a criminal gang blamed for the killing.
Officials said Mr Sarajlic admitted to obstructing legal proceedings against mafia bosses, and undermining investigations into assassinations of prominent Serbian figures in recent years.
"Milan Sarajlic exerted pressure and lobbied within the judiciary," the government said in a statement said on Thursday.
The statement added that Mr Sarajlic was recently paid $150,000 for information about a protected witness.
More arrests expected
Mr Sarajlic's arrest, as well as forced retirement of 35 judges, was part of a major purge of Serbia's judiciary.
On Thursday the head of Serbia's Supreme Court, Leposava Karamarkovic, announced she was standing down under "political and media pressure".
Sarajlic allegedly blocked legal proceedings against mafia bosses
However, despite all efforts, the prime suspects for Mr Djindjic's killing - who include former paramilitary commander Milorad Lukovic- remain at large.
A government official said there would more arrests "in the next few days".
"There still exist remnants of [former President] Slobodan Milosevic's regime," he added.
Mr Djindjic, Serbia's leading pro-Western politician, was killed by a gunman as he stepped out of an armoured car in Belgrade last week.
Authorities blamed the killing on the Zemun Clan - a crime network with alleged links to supporters of Mr Milosevic.
A state of emergency has been imposed.
Serbian Interior Minister Dusan Mihajlovic has said police knew the identities of two of the three people who carried out the assassination.
A photograph of the third man was published in several newspapers on Wednesday.
Under Serbia's law on emergency powers, people can be held for 30 days without charge, and without access to lawyers.