The top UN official in Kosovo says he believes extremists helped lead recent violence that left some 30 people dead.
The Serbian government has declared Sunday a day of mourning
Harri Holkeri said the start of the violence may have been spontaneous, but that it was taken over by extremists.
More than 3,500 Serbs were driven from their homes as a result of clashes between the majority ethnic Albanian population and the Serb minority.
Nato has pledged tight security at the funerals of the Albanian children whose deaths helped spark the crisis.
The funerals are set for Sunday - a day the Serbian government has declared a day of mourning for the Serbs who died in the ensuing violence.
Three Albanian boys drowned near the town of Mitrovica on Tuesday, reportedly after being chased by Serbs. The body of one of them is still missing.
As rumours spread about the boys' deaths, mobs of angry Albanians set alight Serbian Orthodox churches and Serb-owned homes across Kosovo.
A day earlier, a Serb youth was shot and serious injured in what is thought to have been an ethnically-motivated attack near the regional capital Pristina.
The special representative of the UN Secretary General in Kosovo, Harri Holkeri, said he believed Albanian extremists orchestrated the violence.
"Maybe the very beginning was spontaneous but after the beginning certain extremist groups had an opportunity to orchestrate the situation and that is why we urgently are working to get those perpetrators into justice," he said.
KOSOVO: KEY DATES
24 Sept 1998: Nato issues ultimatum to Milosevic to stop crackdown on Kosovo Albanians
24 Mar 1999: Nato begins air strikes against Yugoslavia over Kosovo
10 June 1999: Air strikes suspended after Milosevic agrees to withdraw troops. UN approves peace plan for Kosovo, establishes K-for peace force
11 June 1999: Nato troops enter Kosovo
10 Dec 2003: UN unveils road map on conditions Kosovo must meet by mid-2005 for talks on final status
17 Mar 2004: Serbs and Albanians clash in the worst violence seen since 1999
The BBC's Nick Thorpe in Pristina says the situation in Kosovo has calmed down, but there is still considerable tension.
Nato has sent in extra troops to prevent further violence.
Serbs have been donating more than 30 tons of food, clothes and blankets for their fellow Serbs who were forced out of their homes during the violence.
The UN said at least 3,600 Serbs and other non-Albanians had fled. About 1,100 were being sheltered in camps run by the Nato peacekeeping force, K-For, while the others had gone to Serb areas, such as the town of Gracanica.
Russian President Vladimir Putin on Saturday described the violence in Kosovo as "ethnic cleansing" and called for protection for the Serb minority.
Serbian Prime Minister Vojislav Kostunica has alleged the attacks were "planned in advance and co-ordinated... this was an attempted pogrom and ethnic cleansing" against Kosovo's Serbs.
The clashes were the worst outbreak of violence since Nato forces entered Kosovo in 1999 to end years of ethnic unrest.