Demonstrators in Kosovo's capital Pristina have thrown petrol bombs and stones at police in a protest over the arrest of an opposition MP.
Albin Kurti was held by police after setting off tear gas in parliament last week over a deal between Kosovo and Serbia. He was later released.
About 200 protesters chanted Mr Kurti's name as they threw missiles at the ranks of police officers.
Police fired tear gas and advanced in an attempt to push the protesters back.
Mr Kurti was questioned by police and released later on Monday.
"We will not give up. Let's stay united," he was quoted as saying to his supporters by the AFP news agency.
His stunt in parliament was part of a protest by opposition MPs against the deal with Serbia.
The EU-brokered agreement grants more powers to the mainly Serb areas of Kosovo. Opposition MPs say it will deepen the ethnic divide and increase Serbia's power in the country.
As well as releasing tear gas, opponents of the deal have blown whistles and thrown eggs to disrupt recent parliamentary sessions.
Kosovo's ethnic Albanians broke away from Serbia in an armed revolt in 1999, and then unilaterally declared independence in 2008.
Belgrade rejected the move and still considers the breakaway territory as its southern province.