At least 30 peacekeepers from the NATO mission in Kosovo (KFOR) were injured after Serb protesters demonstrating against the election of elected ethnic Albanian mayors clashed in the country's north.

The KFOR mission said it had faced "unprovoked attacks" while countering a hostile crowd after demonstrators clashed with police and tried to force their way into a government building in the northern town of Zvecan.

Serbian President Aleksandar Vucic said 52 Serbs were hurt, three seriously, while one was "wounded with two gunshots by (ethnic) Albanian special forces."

Hungary's defense minister said on Facebook that "more than 20 Hungarian soldiers" were among the wounded, with seven in serious but stable condition.

Italy's foreign minister said three of its soldiers were seriously wounded, and the country's Prime Minister Giorgia Meloni joined NATO in calling for "all parties to take a step back to lower tensions."

Kosovo's Serbs had boycotted last month's elections in northern towns, which allowed ethnic Albanians to take control of local councils despite a minuscule turnout of under 3.5% of voters.

Kosovan Prime Minister Albin Kurti's government officially installed the mayors last week, defying calls to ease the tensions between the European Union and the United States, which have both championed the territory's 2008 independence from Serbia.

Many Serbs are demanding the withdrawal of Kosovo police forces – whose presence in northern Kosovo has long sparked resistance – as well as the ethnic Albanian mayors they do not consider their true representatives.

Fractures and burns

Early Monday, groups of Serbs clashed with Kosovo police in front of the municipal building in Serb-majority Zvecan. They tried to enter, after which law enforcers responded by firing tear gas, according to an AFP journalist at the scene.

At first, NATO-led peacekeepers in the KFOR mission tried to separate protesters from the police but later started to disperse the crowd using shields and batons, an AFP journalist saw.

Several protesters responded by hurling rocks, bottles and Molotov cocktails at the soldiers but were quickly repelled a few hundred meters away from the Zvecan municipal building.

"While countering the most active fringes of the crowd, several soldiers of the Italian and Hungarian KFOR contingent were the subject of unprovoked attacks and sustained trauma wounds with fractures and burns due to the explosion of incendiary devices," KFOR said in a statement.

Eleven Italian soldiers were injured, with "three in a serious condition," Foreign Minister Antonio Tajani said.

"We will not tolerate further attacks against KFOR," said Meloni. "It is essential to avoid further unilateral actions by the Kosovo authorities and for all parties to take a step back to lower tensions."

NATO strongly condemned the "unprovoked" attacks against KFOR troops, adding that such actions were "totally unacceptable."

"Violence must stop immediately. We call on all sides to refrain from actions that further inflame tensions and to engage in dialogue," NATO said.

The Commander of the KFOR Mission, Division General Angelo Michele Ristuccia, slammed the "unacceptable" attacks and underlined that KFOR will "continue to fulfill its mandate impartially."

Kosovo police said "organized" demonstrators rallied in northern Kosovo towns, home to many ethnic Serbs who reject Kosovo's independence from Serbia.

"The protesters, using violence and throwing tear gas, tried to cross the security cordons and make a forced entry into the municipality facility" in Zvecan, Kosovo police said in a statement.

"Police were forced to use legal means, such as (pepper) spray, to stop the protesters and bring the situation under control."

Kosovo declared independence from Serbia in 2008. However, Belgrade and its key allies Russia and China have refused to recognize it, effectively preventing Kosovo from having a seat at the United Nations.

Serbs in Kosovo remained largely loyal to Belgrade, especially in the north, where they make up a majority and reject every move by Pristina to consolidate its control over the region.

International concern

KFOR said it had bolstered its presence in northern Kosovo following the latest developments and urged Belgrade and Pristina to engage in an EU-led dialogue to reduce tensions.

"We call on all sides to refrain from actions that could inflame tensions or cause escalation," KFOR said.

Police had already used tear gas Friday to disperse Serbs in northern Kosovo who protested the installation of the mayors.

Belgrade responded by alerting its army and ordered forces towards the Serbian border with Kosovo.

In a visit to Kenya, Russia's foreign minister Sergei Lavrov said, "Serbs are fighting for their rights in northern Kosovo."

"A big explosion is looming in the heart of Europe, where NATO in 1999 carried out an aggression against Yugoslavia," Lavrov said, referring to the 1999 NATO intervention against Belgrade that effectively ended the war between Serb forces and ethnic Albanian guerrillas.

The U.S. ambassador and EU envoy have summoned the ethnic Albanian mayors to a meeting in Pristina in a bid to ease tensions.

Two media teams from Pristina reported that protesters had slashed their tires and spray-painted their vehicles, while a local journalists' association called on law enforcers to provide a safe working environment for the media.

After his first-round victory at the French Open on Monday, Serbian tennis superstar Novak Djokovic penned the message "Kosovo is the heart of Serbia. Stop the violence" on a television camera.

"Kosovo is our cradle, our stronghold, the center of the most important things for our country," Djokovic told reporters.

"I am against war, violence and conflict of any kind and have always publicly shown that. Of course, I sympathize with all people, but what is happening with Kosovo is a precedent in international law."