Kosovo police on Monday arrested a senior Serbian official in the flashpoint town of Mitrovica, raising fresh tensions between the former foes who are trying to relaunch a dialogue.
Marko Djuric, Belgrade's chief negotiator for Kosovo - a former Serbian province that proclaimed independence in 2008 -- was arrested after he crossed into the disputed territory and travelled to Mitrovica in defiance of a ban, a police spokesman said.
Kosovo President Hashim Thaci in a statement called for calm and said Djuric was escorted by police to a "border crossing point between Kosovo and Serbia."
Shortly before 7:00 pm (1900 GMT) Serbian state-run RTS television announced Djuric's return to Serbia.
Serbian President Aleksandar Vucic labelled the arrest an abduction.
"All those who have participated in this abduction will be held accountable before Serbian state bodies," he told reporters in Belgrade.
"They beat him ... dragged him on the streets of Pristina under boos to complete the humiliation."
After the arrest, Djuric was taken to a police centre in Pristina, a police spokesman told AFP. Kosovo authorities said he had not obtained entry authorisation.
Serbian officials visiting Kosovo commonly seek Pristina's approval before visiting areas with an ethnic Serb population.
Hooded police holding automatic weapons and accompanied by armoured vehicles, were deployed from the Serbian border to Mitrovica to prevent several Serbian officials from entering Kosovo, according to an AFP corespondent.
Nearly 20 years after the 1998-1999 war between Serb forces and Kosovo pro-independence ethnic Albanian guerillas, Mitrovica remains divided between ethnic Serbs, living north of the Ibar river, and ethnic Albanians, south of it.
International forces are still deployed in the town.
Today Kosovo, which has a population of 1.8 million, is home to some 120,000 ethnic Serbs.
A public round-table in Mitrovica attended by Djuric was aimed at "internal dialogue" over the Kosovo issue, which is key to Belgrade's bid to join the European Union.
In the hall where it was held a Serbian flag was on display.
Police had to battle their way through the hall where Djuric was attending the meeting, using tear gas to disperse dozens of residents trying to intervene.
He was then taken to the police station in Pristina, where he was dragged by police in front of the cameras and insulted by residents, according to AFP journalists.
Although there have been no serious inter-ethnic incidents in Mitrovica in recent years, the town remains tense.
The fragile situation was illustrated by the murder of moderate Kosovo Serb politician Oliver Ivanovic in January.
A probe has failed to shed light on the murder.
Monday's arrest is the most serious incident since Belgrade sent a train to Kosovo in January 2017 painted in the Serbian flag's colours with a sign reading "Kosovo is Serbia" in multiple languages.
Pristina labelled it a "provocation", but Vucic halted it before the border.
The arrest and expulsion of Djuric took place after Vucic and Thaci met in Brussels on Friday to restart the EU-sponsored talks on normalisation of ties, which have been deadlocked for the past two years.
Thaci said the incident "should not interfere with ... the dialogue between the two countries, the efforts for normalisation, good neighbourly relations and reconciliation between Kosovo and Serbia."
About 115 countries have recognised Kosovo's independence over the past 10 years. However, Serbia and dozens of other states, including its ally Russia, have not.
The 1998-1999 Kosovo conflict claimed 13,500 lives.