The European Union informed the UN Security Council Tuesday that security in parts of Kosovo has deteriorated, citing last week's incident in which one protester was killed in the Serb enclave in Kosovo, dpa reported.
Serbia said some 3,000 ethnic Serbs held a protest Friday in Mitrovica, in north-western Kosovo, and were attacked with bombs. One person was killed and a dozen others were injured.
Serbian President Boris Tadic, who attended the council meeting in New York, condemned the incident.
The EU representative, Yves de Kermabon, said his organization has condemned the incident and called for an investigation.
"The security has deteriorated," de Kermabon said. "We are aware of the tensions and call on the authorities in Pristina to investigate."
Tadic accused "ethnic Albanian secessionists" of trying to set up a Kosovo government office in the "Serbian town of North Mitrovica," which prompted the Serb ethnic protest.
Mitrovica is an ethnically divided town 35 kilometres north-west of Pristina. The Kosovo war ended 11 years ago, but Mitrovica remains tense and prone to spates of violence.
"The ethnic Albanian authorities have to be told what the consequence will be - should they try unilateralism again," Tadic said. "Otherwise, Serbia will have no choice but to reassess its relations with the international province in the province."
Kosovo, a former Serb province, unilaterally declared independence in February 2008. Belgrade, backed by Moscow, rejected the move and took the case before the UN International Court of Justice.
Tadic said the court would make a decision soon on whether Kosovo's declaration of independence was legal. He said Belgrade will never accept an independent Kosovo.
The UN Security Council has not recognized that independence. But more than 40 countries, including many Europeans and the United States, have done so.
The EU and NATO provide legal and security assistance to Pristina while a small UN mission maintains the UN presence there.