Serbian police have arrested a senior special police officer on suspicion of assassinating Serbian Prime Minister Zoran Djindjic.
Jovanovic served with special police during the wars of the 1990s
Mr Djindjic's successor as prime minister, Zoran Zivkovic, said the man was a deputy commander of the Unit for Special Operations (JSO), Zvezdan Jovanovic, aged 38.
The JSO was disbanded on Tuesday by Serbian authorities and its former members have been ordered to hand in their arms, uniforms and official identity cards.
"Police have identified the person who, there are good grounds to suspect, fired at late Prime Minister Zoran Djindjic," he told a news conference.
"He was arrested yesterday and has been detained for further investigation."
Mr Djindjic was killed by a sniper's bullet outside government buildings in Belgrade on 12 March.
Just hours after the killing, Serbian authorities blamed a criminal gang led by a former JSO commander Milorad Lukovic.
Mr Zivkovic said the current JSO commander, Dusan Maricic, had been removed from his position and detained for further investigation.
He also said police had found a German-made Heckler Koch G3 sniper rifle, which they believe to be the murder weapon.
This is not the end of the investigation - it will be ended once all involved have been arrested and brought to justice
Prime Minister Zoran Zivkovic
More than 1,000 people have been arrested and nearly 400 charged since the killing.
Mr Lukovic and another chief suspect, Dusan Spasojevic, are still at large.
"This is not the end of the investigation. It will be ended once all involved have been arrested and brought to justice," said Mr Zivkovic.
Under the state of emergency imposed after Mr Djindjic's killing, police are able to carry out arrests without warrants, and to keep suspects in detention for 30 days without charge.
Police have said that the Djindjic hit squad consisted of three people dressed as workers, who took up position in a building opposite the government offices.
Mr Djindjic was killed by one shot to the chest as he got out of his car on crutches.
Mr Zivkovic said the sniper suspects had links to the Zemun organised crime clan, which is led by Mr Lukovic.
Zoran Djindjic made enemies of criminals and hardline nationalists
He said another man suspected of aiding the sniper, Sasa Pejakovic, had also been arrested.
Serbian officials at first suggested that Mr Djindjic had been killed because he had declared war on organised crime.
However, they have also noted that his readiness to send war crimes suspects including Slobodan Milosevic to the international war crimes tribunal, angered hardline nationalists.
The JSO has been blamed for numerous atrocities committed during the Balkan wars.
Zvezdan Jovanovic was a member of the paramilitary unit during the wars of the 1990s.