The European Union and the United States are concerned about the situation in the north of Kosovo and urge the rival parties to de-escalate tensions, they said in a joint statement on Wednesday.
About 50,000 Serbs living in ethnically divided northern Kosovo refuse to recognise the government in Pristina or the status of Kosovo as a country separate from Serbia. They have the support of many Serbs in Serbia and its government.
Last month Serb representatives left state institutions, including the police and judiciary, over the Kosovo government's decision to replace Serbian issued car licence plates.
The joint statement said the United States and the EU were working with Serbian President Aleksandar Vucic and Kosovo's Prime Minister Albin Kurti to find a political solution in order to defuse the tensions.
"We call on everyone to exercise maximum restraint, to take immediate action to unconditionally de-escalate the situation, and to refrain from provocations, threats, or intimidation," it said.
Kosovo closed its biggest border crossing with Serbia on Wednesday after protesters blocked it on the Serbian side to support their ethnic kin in Kosovo in refusing to recognise the country's independence.
A former Kosovo Serb policeman was arrested on Dec. 10 for assaulting a serving police officer. The arrest triggered violent protests by Kosovo's Serb minority. He will be released from custody and put under house arrest, a court spokesperson said on Wednesday.
Albanian-majority Kosovo declared independence from Serbia in 2008 with the backing of the West following a 1998-99 war in which NATO intervened to protect ethnic Albanian citizens.
(Reporting by Kanishka Singh in Washington, Editing by Angus MacSwan)
