Russia on Saturday blamed Kosovo, the United States and European Union for escalating tensions in the Balkans and said it was watching with concern after violent clashes between Kosovan police and protesters opposed to ethnic Albanian mayors.

The United States and allies on Friday rebuked Kosovo, saying the use of force to install mayors in ethnic Serb areas undermined efforts to improve troubled relations with neighbouring Serbia. NATO on Saturday urged Kosovo to dial down tensions.

The clashes led Serbian President Aleksandar Vucic on Friday to place the army on full combat alert and ordered units to move closer to the border.

"We decisively condemn Pristina's provocative steps, which have brought the situation close to the hot phase and directly threaten the security of the whole Balkans region," Russia's foreign ministry spokeswoman Maria Zakharova said in a statement.

"The responsibility for this lies fully with the United States and the European Union," she said, adding that rebukes of Kosovo by "Western mediators" had come too late.

Serbia and its traditional ally Russia do not recognise Kosovo's independence, and Moscow has blocked the country's bid to become a member of the United Nations. Serbia still considers Kosovo part of its territory.

(Reporting by Alexander Marrow; Editing by Conor Humphries)