The Kosovo-Serbia border was blocked for a third straight day by ethnic Kosovo Serbs protesters on Wednesday.
Trucks have parked on the road to the Jarinje and Brnjak border crossing where small groups of Serbs have spent the night in tents.
Kosovo police fired tear gas at the protesters on Monday, but the blockade has remained at the frontier.
It comes as Kosovo deployed additional police to implement a rule to remove Serbian license plates from cars entering the country.
The two sides agreed in European Union-mediated talks in 2014 to allow free traffic. However, Kosovo officials said the deal has expired and only proper Kosovo symbols are now valid in the territory.
Pristina stated that, from Monday, licence plates issued in Serbia will be replaced with temporary ones and that the additional police were deployed to implement the "reciprocity" action.
Serbia's police have for years been taking off registration plates from Kosovo-registered cars entering Serbia, and the latest move by Kosovo authorities appears to be a tit-for-tat move.
But there are fears that the recent road blocks may unleash much deeper tensions between the two Balkan neighbours.
Serbia does not recognise its former province of Kosovo as a separate state and considers the mutual border only as an "administrative" and temporary boundary.
In Belgrade, Serbian President Aleksandar Vucic called an emergency meeting for Tuesday of the state national security council and described Kosovo’s car license plates decision as a “criminal action”.
Top Kosovo Serb official Goran Rakic described the latest move as "a direct threat" against Serbs living in Kosovo, saying they have informed EU mediator Miroslav Lajcak and other international officials about the new developments.
"This (protest) is a reaction by the people who are worried about their future, their children, and their families," said Rakic. "People are anxious and frightened."
Kosovar Prime Minister Albin Kurti held a meeting with the western ambassadors on Tuesday, and stated that the decision was "not a provocation or discrimination against anyone".
On Wednesday Kurti called on Serbs to move vehicles away "because they are blocking themselves"
"Our offer is very practical, let’s lift the temporary plates, in Serbia and in Kosovo ... We are for dialogue," he said at a government meeting.
The EU and US urged Kosovo and Serbia to “immediately, without any delay” exercise restraint and refrain from unilateral actions.
Thousands of people were killed and over a million were left homeless after a 1998-1999 bloody crackdown by Serbian troops against Kosovo Albanian separatists. The war ended only after a NATO intervention.