Serbian security forces on the border with Kosovo were placed in a state of “full combat readiness”.
The order was given by Serbian Interior Minister Bratislav Gasic, who said he was acting on instructions from President Aleksandar Vucic so that “all measures are taken to protect the Serbian people in Kosovo”.
Kosovo did not react to this decision.
It comes after weeks of escalating tensions between the two sides, with ethnic Serbs saying they are being harassed by majority ethnic Albanians in Kosovo.
The war in Kosovo ended in 1999, with the intervention of NATO.
Kosovo declared independence in 2008 but Serbia refuses to acknowledge him and has repeatedly warned that he will protect local Serbs “by all means” if they are attacked.
Last month, ethnic Serb mayors, judges and police officers in northern Kosovo resigned in protest at the Kosovo government’s decision to replace Serb-issued car license plates with those issued by Pristina.
Thousands of Kosovo Serbs marched this month demanding the Albanian majority government withdraw the police from the north.
Since December 10, local Serbs have erected nine roadblocks in the northern region of Kosovo, where around 50,000 of them live.
On Sunday, a shootout took place near a NATO peacekeeping patrol in one of the northern towns and, although there were no injuries, NATO said that she investigated and called for calm.
The European Union tried to mediate between the two sides and Serbia, which was armed with the help of Russian support, agreed to talks.
