Police in Kosovo have fired tear gas in a clash with protesters angered by recent talks aimed at improving ties between Serbia and its former province.
At least 20 people, including police, were injured and dozens of protesters arrested in the capital Pristina.
The rally was organised by Kosovo's Self-Determination party, which opposes any talks with Belgrade.
Serbia - which lost control of Kosovo after a war in 1999 - does not accept its independence.
Kosovo's statehood has been recognised by some 90 countries, including the US and most of the EU members.
On Monday, the demonstrators chanted "Shame!" and "No bargain with Serbia!" as they tried to push through a police cordon around the office of Kosovo's Prime Minister Hashim Thaci.
"Serbia is an abnormal state and we don't want to 'normalise' our relations," Self-Determination leader Albin Kurti told the AFP news agency.
Some in the crowds threw stones at police, who responded by firing tear gas and pepper spray.
Mr Thaci condemned the protesters, saying they were "opposed to progress in Kosovo".
"They follow the same agenda as the opponents of Kosovo's independence," he added.
The protest was organised following last week's talks between Mr Thaci and his Serbian counterpart Ivica Dacic in Brussels - the first direct political contact between the two sides since Kosovo proclaimed independence in 2008.
EU foreign affairs chief Catherine Ashton, who chaired the talks, said afterwards that both leaders had undertaken to work together to normalise relations.
She said they had agreed to "meet again soon... to improve the lives of people and help solve problems and, in so doing, bring Serbia and Kosovo closer" to the EU.
Tension between Kosovo's ruling ethnic Albanian majority and remaining ethnic Serbs has resulted in violence in recent years, notably along the northern border with Serbia.
EU leaders granted Serbia "candidate status" at a summit in Brussels in June, but stressed it must find a solution to the Kosovo issue before any further progress towards EU membership could be made.