NATO confirmed on Tuesday that it was deploying more forces to northern Kosovo after 30 of its forces were injured in clashes with ethnic Serb protesters, while the European Union called for an urgent de-escalation of tensions.

NATO Secretary-General said the attacks on NATO forces in Kosovo are "unacceptable" and "must stop".

Admiral Stuart Munsch, the commander of the Allied Force Command in Naples, indicated that the move was a "prudent measure to ensure that KFOR (the NATO-led Kosovo Force) has the capabilities it needs to maintain security."

The US-led military alliance added in a statement from its southern Italian base that an extra multinational battalion of reserve forces had also been put on notice to be ready to reinforce KFOR if necessary.

The situation in the northern Kosovo town of Zvecan remained tense on Tuesday as ethnic Serbs gathered outside the town hall. Kosovo police had repelled them with tear gas before the NATO-led forces intervened.

The soldiers at first tried to separate protesters from the police but later tried to disperse the crowd using shields and batons, an AFP journalist said.

Many Serbs are demanding the withdrawal of Kosovo police forces, as well as the ethnic Albanian mayors they do not consider their true representatives.

Kosovo's ethnic Serb minority boycotted local elections in the north in April, allowing ethnic Albanians to take control of the local councils despite a tiny turnout of less than 3.5%.

On May 26, the Kosovo police seized administrative buildings in the Serbian municipalities of Zvecan, Zubin Potok, and Leposavic, escalating the situation in northern Kosovo and Metohija.

The police attempted to enable the newly elected mayors to take office after winning the elections.

Read more: NATO forces wounded during clashes in Kosovo

Borrell urges Kosovo, Serbia leaders to de-escalate tensions

EU foreign policy chief Josep Borrell on Tuesday urged the leaders of Kosovo and Serbia to immediately de-escalate tensions, saying that the clashes were "absolutely unacceptable".

Borrell said he had spoken to Kosovo's Prime Minister Albin Kurti and Serbian President Alexander Vucic to tell them to avoid any "further unilateral action."

"I asked both parties to urgently take measures to de-escalate tensions immediately and unconditionally," the EU foreign policy chief indicated.

He considered that Kosovo's authorities needed to suspend police operations focused on municipal buildings in north Kosovo and ethnic Serb protesters should stand down.

Elsewhere, Borrell warned that the EU was "discussing possible measures to be taken if the parties continue to resist proposed steps towards de-escalation."

Vucic highlighted that 52 demonstrators were injured in Monday's clashes, including three seriously.

On its part, KFOR had said the 30 hurt forces -- from Hungary and Italy, according to their governments -- had injuries including "fractures and burns from improvised explosive incendiary devices."

It claimed that the soldiers had responded to "unprovoked attacks of a violent and dangerous crowd."

"Both parties need to take full responsibility for what happened and prevent any further escalation, rather than hide behind false narratives," the NATO-led Kosovo Force pointed out.

Kosovo declared its independence from Serbia in 2008, but Belgrade and Moscow have refused to recognize it.

It is noteworthy that ethnic Serbs make up around six percent of the population in Kosovo, especially in the north where they are a majority.

After last month's election boycott, Kosovo's Prime Minister Albin Kurti installed the newly elected ethnic Albanian mayors.

"One-sided moves from Pristina bring violence against the Serb community, which distances us from lasting peace and stability in the region," Serbian President Alexander Vucic wrote on Instagram after a meeting with Western diplomats.

"Swift withdrawal of false mayors and members of Pristina's so-called special forces is a condition of preserving peace in Kosovo," Vucic underlined.

Read more: Purpose of escalations in Kosovo to clash Serbia with NATO: Vucic

KFOR has become source of destabilization in region: Zakharova

In the same context, Russian Foreign Ministry Spokesperson Maria Zakharova considered in a statement on Tuesday that the KFOR has become a source of unjustified violence and destabilization in the region.

Zakharova pointed out that "the crisis situation in the municipalities of Zvecan, Zubin Potok, and Leposavic, which could have been resolved through a calm compromise, was a tough nut to crack for the NATO ‘peacekeepers’ in Kosovo."

"They not only showed their unprofessionalism, but also became a source of unnecessary violence and a factor of escalation," she added.

The Russian diplomat indicated that "those who are supposed to protect the local Serbian majority from the arbitrariness of the Kosovars ended up siding with the xenophobic aspirations of Pristina and have essentially become accomplices of terror - taking up the role of personal security of the self-appointed government of Kosovo’s Albanians who have holed up in administrative buildings."

The Russian spokesperson stressed that Russia is urging the West to quit spreading "false propaganda" and refrain from blaming the tensions on "desperate Serbs who peacefully, without weapons, try to defend their legitimate rights and freedoms."

"This is a case when intermediaries from the US and the EU should work up the courage to look in the mirror," she added.

Zakharova pointed out that the region requires serious action to stabilize the situation, not partial measures such as the US suggestion to relocate the freshly elected "mayors" from municipal facilities to other locations.

"The number one task is still the establishment of a community of Serbian municipalities in the region in its original form, which was enshrined 10 years ago in written agreements between Belgrade and Pristina under the guarantee of Brussels," the Russian Foreign Ministry Spokesperson stressed.

"This is a key condition for dialogue, and is the only chance to ensure stability and security in the region," she affirmed.

Read more: NATO urges Kosovo to de-escalate with Serbia