The prominent politician was close to his party office in the northern town of Mitrovica where he was shot at least five times.
A leading Serb politician in northern Kosovo was shot and killed on Tuesday morning, raising ethnic tensions in the region and halting EU-mediated talks between Kosovo and Serbia on the day they were due to resume.
Assailants opened fire on Oliver Ivanovic close to the offices of his political party in the Serb-controlled northern city of Mitrovica. He was taken to a hospital but doctors were unable to save him.
The doctors said that Ivanovic received at least five gunshot wounds to his upper torso. The assailants escaped in a car that was later found burned out. Kosovo police sealed off the area of the shooting and were looking for the attackers.
Attack might raise tensions
The Serb delegation at EU talks due to start in Brussels on Tuesday immediately left to return to Belgrade.
Delegation leader Marko Djuric said that "whoever is behind this attack ... whether they are Serb, Albanian or any other criminals, they must be punished."
Ivanovic, 64, was one of the key politicians in Serb-dominated northern Kosovo, a former Serbian province where tensions remain high a decade after it declared independence.
Serbia does not recognise the independence of its former province and the killing is likely to raise tensions between ethnic Albanians and minority Serbs in the region.
In Belgrade, Serbian President Aleksandar Vucic called a top state security meeting to discuss the shooting, and was later due to address the public.
In Pristina, the Kosovo government strongly denounced the slaying and said it considers it to be a challenge to "the rule of law and efforts to establish the rule of law in the whole of Kosovo territory."
A Kosovo court convicted Ivanovic of war crimes during the 1998-99 war. That verdict was overturned and a retrial was underway.
Ivanovic was considered a moderate opposition Serb politician. In July, his car was set on fire in Mitrovica, the Serb stronghold in northern Kosovo.