Kosovar police reported outbreaks of overnight violence in the largely ethnic Serb part of the country on Sunday.
They described scenes of explosions, roadblocks and gunfire after hundreds of Serbs gathered on Saturday morning to protest the arrest of a former police officer following a mass exodus of Serb officers from the force last month.
Local police say they were targeted by three firearm attacks. A contingent of EU police officers also said a stun grenade was thrown toward them.
"This attack, as well as the attacks on Kosovo Police officers, are unacceptable," the EU's rule of law mission (EULEX) said in a statement.
The EU's foreign policy chief Josep Borrell also responded to the violence on Twitter, saying the "EU will not tolerate attacks on EULEX."
"Barricades must be removed immediately by groups of Kosovo Serbs," he said, adding that "All actors must avoid escalation."
Local election postponed
The tensions stem from a dispute over banning Serbian license plates in Kosovo which led to hundreds of local mayors, judges and police officers resigning in protest.
As a result, Pristina called for elections to take place on December 18 which the main Serb political party said it would boycott.
Kosovar President Vjosa Osmani delayed the vote to April 23 on Saturday as the first roadblocks on the main border crossings with Serbia were set up.
France, Germany, Italy, the UK, the US and the EU all welcomed the postponement, calling it a "constructive decision" that "advances efforts to promote a more secure situation in the north."
German Foreign Minister Annalena Baerbock said, "Suggesting sending Serbian forces to Kosovo is completely unacceptable. So are the latest attacks on [EULEX Kosovo]," referring to Serbian President Alexander Vucic's remarks on requesting the presence of NATO troops in Kosovo.
Decades of tension
Kosovo gained independence from Serbia in 2008 following a war in 1998-1999 that only ended with NATO intervention, although this has never been officially recognized by Belgrade.
The Serb minority in the north of Kosovo — which Belgrade has called on to defy orders from Pristina — accounts for around 120,000 of the total population of around 1.8 million, most of whom are ethnically Albanian.
In response to the rising tensions, Serbian President Vucic said he would request permission from NATO peacekeepers to send some 1,000 Serbian troops into the fragile region — although he conceded there was "no chance of the request being approved."
Kosovar Prime Minister Albin Kurti responded by accusing Serbia of "threatening Kosovo with aggression."
"We do not want conflict, we want peace and progress, but we will respond to aggression with all the power we have," he wrote on Facebook.
Vucic seeks deescalation
Later on Sunday, Vucic urged the release of all arrested Serbs from northern Kosovo. At the same time, he said Serbia is seeking to defuse tensions in the restive region.
After a meeting of the National Security Council, Vucic said Kosovo Serbs must not harm NATO troops and members of the EU mission there.
"No one, under no circumstances should be involved in attacks ... on Eulex and KFOR," he said.
dh, ab/ar (AFP, AP, Reuters)