UPDATE 1 - NATO deploys additional forces in Kosovo as tensions run high

"In response to recent unrest and the injury of 30 members of NATO’s Kosovo Force, NATO has directed the deployment of the Operational Reserve Forces (ORF) for the Western Balkans, which was on a seven-day readiness-to-deploy status," NATO said on Twitter.

"An additional multi-national battalion of reserve forces has been ordered to decrease their readiness-to-deploy status from fourteen days to seven days, in order to be ready to reinforce KFOR if necessary," the Alliance said in another post.

EU High Representative Joseph Borrell said he had spoken to both Kosovo's prime minister Albin Kurti and Serbia's president Aleksandar Vucic, urging them to de-escalate tensions "immediately and unconditionally".

“Member States are being informed about the developments and discussing possible measures to be taken if the Parties continue to resist proposed steps towards de-escalation,” Borrell said in a statement.

KFOR said earlier on Tuesday that 30 of their soldiers were injured as they confronted ethnic Serb protestors in the city of Zvecan.

“KFOR always operates with firmness and restraint, within strict Rules of Engagement. In this case, it responded to the unprovoked attacks of a violent and dangerous crowd, whilst carrying out its UN mandate in an impartial manner,” KFOR said in a social media post.

The injuries sustained by the soldiers are not life-threatening, KFOR noted.

The situation seems to have calmed but remains delicate, Kosovo police said in a statement on Tuesday.

KFOR increased its presence in the municipalities of Northern Mitrovica, Leposaviq, Zvecan and Zubin Potok, in response to ethnic Serb attempts to block the newly elected mayors from entering municipal buildings on Friday. The mayors were selected in preemptive elections with a 3.45% participation rate, after the Serbian party decided to boycott elections, local media reported in April.

Last week, president Aleksandar Vucic put Serbia's army on full combat alert. Serbian army units have been deployed close to the Kosovo border, Serbia's defence minister Milos Vucevic has said.

Reacting to rising tension, representatives of the United States and the European Union urged Kosovo's authorities to show restraint.

“We condemn Kosovo’s decision to force access to municipal buildings in northern Kosovo despite our call for restraint. We call on Kosovo’s authorities to immediately step back and de-escalate, and to closely coordinate with EULEX and KFOR,” France, Italy, Germany, the United Kingdom and the US said in a joint statement on May 26.