The Serbian Prime Minister Vojislav Kostunica has said Kosovo will always remain part of Serbia, during a visit to the ethnically-divided province.
The Serbian PM was said by the UN to be on a 'private' visit
He told a crowd of local Serbs Belgrade would guarantee their interests in UN-brokered talks on Kosovo's future.
"No one is on firmer, truer ground in the talks on Kosovo's final status than Serbia," Mr Kostunica said.
Security was tight for Mr Kostunica's visit to the province, whose ethnic Albanian majority wants independence.
The Serbian leader was visiting Kosovo to mark the anniversary of a 14th Century battle, in which the army of Serbia's Christian Prince Lazar was defeated by Ottoman invaders.
Traditional Serbs regard the defeat at Kosovo Polje as a critical moment in the history of their faith - and Kosovo as the crucible of their nationhood.
Some 1,000 Serbs gathered at an Orthodox Christian monastery at Gracanica to greet Mr Kostunica on Wednesday.
"There is no better place to repeat what all Serbs should know - that Kosovo always was and always will be part of Serbia," he said, drawing cheers and chants from the crowd.
He told the audience Belgrade would reject any attempt to prise Kosovo away from Serbia in negotiations.
Mr Kostunica took a short walk around the stone courtyard of the monastery, accompanied by priests and a brass band, as a Nato helicopter hovered overhead.
The UN had billed Mr Kostunica's visit as a private one - but his presence nonetheless attracted protests from a Kosovo Albanian pressure group, which has been calling for the province's leaders to abandon talks and declare independence.
More than 100 protesters were arrested in scuffles with police.
Talks on future
Although it technically remains part of Serbia, Kosovo has been administered by the UN since 1999, when Nato air strikes drove out Serb security forces accused of persecuting the Albanian population.
Thousands of Kosovo's minority Serbs fled later amid sporadic clashes with the Albanian majority.
The security situation has improved, but Nato troops deploy to Serb areas when violence flares up again.
Diplomats say talks on the province's future, currently under way, are likely to bring some form of independence for Kosovo - as desired by the Albanians but opposed by the Serbs.