Russia's ambassador to Nato, Dmitry Rogozin, has warned that Russia could use military force if the Kosovo independence dispute escalates.
Czech Nato troops went to prevent further Serb violence
"If the EU develops a unified position or if Nato exceeds its mandate set by the UN, then these organisations will be in conflict with the UN," he said.
In that case Russia would "proceed on the basis that in order to be respected we need to use brute force", he said.
Many EU members have recognised Kosovo, but several oppose recognition.
Russia, a permanent member of the UN Security Council, backs Serbia, which has condemned the independence declaration issued by the Kosovo parliament on 17 February.
On Tuesday members of the Serb minority in Kosovo attacked two border posts staffed by UN personnel and Kosovo police.
The violence led the Nato troops in Kosovo - known as K-For - to reinforce the border with Serbia.
Kosovo's majority ethnic Albanians are following a plan drawn up by UN special envoy Martti Ahtisaari for "supervised independence", which was rejected by Serbia.
Russian media outcry
The EU will soon deploy 2,000 officials to strengthen law and order in Kosovo, which has a population of about two million. Russia argues that the mission has no legal basis.
There has been a furious reaction in some Russian media to Kosovo's declaration of independence.
A commentary in the Vesti Plus analytical programme, on state-run television, called the assassinated former Serbian Prime Minister, Zoran Djindjic, a Western puppet who had "received a well-deserved bullet".
It said Djindjic had sold national heroes to the International War Crimes Tribunal in The Hague.
The programme concluded that Serbia - and not only Serbia - must now decide whether to acquiesce in what has happened, or resist.