The Kosovo government has postponed implementing a decision that would oblige Serbs in the north of the country to apply for car number plates issued by Pristina institutions over tensions between police and communities that set roadblocks.
The protesters late on Sunday parked trucks filled with gravel and other heavy machinery on roads leading to the two border crossings, Jarinje and Bernjak, in a territory where Serbs form a majority.
Kosovo police said they had to close the border crossings.
"The overall security situation in the northern municipalities of Kosovo is tense," NATO-led mission to Kosovo KFOR said.
In Moscow, Russian foreign ministry spokeswoman Maria Zakharova blamed the heightened tension on what she called "groundless discriminatory rules" imposed by Kosovo authorities
Fourteen years after Kosovo declared independence from Serbia, some 50,000 Serbs living in the north use number plates and documents issued by Serbian authorities, refusing to recognise institutions under the capital, Pristina.
Kosovo has been recognised as an independent state by more than 100 countries but not by Serbia or Russia.
The government of Prime Minister Albin Kurti said it would give Serbs a transitional period of 60 days to get Kosovo number plates, a year after giving up trying to impose them due to similar protests.
The government also decided that as of August 1, all citizens from Serbia visiting Kosovo would have to get an extra document at the border to grant them permission to enter.
A similar rule is applied by Belgrade authorities to Kosovars who visit Serbia.
But following tensions on Sunday evening and consultations with EU and US ambassadors, the government said it would delay its plan for one month and start implementation on September 1.
Earlier on Sunday, police said shots were fired "in the direction of police units but fortunately no one was wounded".
It also said angry protesters beat up several Albanians passing on the roads that had been blocked and that some cars had been attacked.
Air raid sirens were heard for more than three hours in the small town of North Mitrovica inhabited mainly by Serbs.
A year ago, after local Serbs blocked the same roads over number plates, Kosovo's government deployed special police forces and Belgrade flew fighter jets close to the border.
Tensions between the two countries remain high and Kosovo's fragile peace is maintained by a NATO mission which has 3770 troops on the ground.
Italian peacekeepers were visible in and around Mitrovica on Sunday.
Australian Associated Press
