On Monday, approximately 25 NATO peacekeeping soldiers defending three town halls in northern Kosovo were injured in clashes with Serb demonstrators, while the president of Serbia placed the army on the highest combat alert level.
KFOR, the peacekeeping force in Kosovo commanded by NATO, condemned the violence.
"While countering the most active fringes of the crowd, several soldiers from the Italian and Hungarian KFOR contingent were subjected to unprovoked attacks and sustained trauma wounds with fractures and burns due to the explosion of incendiary devices," the statement read.
The defense minister of Hungary, Kristof Szalay-Bobrovniczky, stated that seven Hungarian soldiers were severely injured and would be treated in Hungary. He said 20 personnel were injured. During the confrontations, Italian soldiers were also injured.
Giorgia Meloni of Italy said, "What is occurring is unacceptable and irresponsible." "It is imperative that the Kosovar authorities refrain from further unilateral actions and that all parties involved immediately take a step back to defuse the tensions."
According to Serbian President Aleksandar Vucic, 52 Serbs were injured, including three severely hurt.
President Vjosa Osmani of Kosovo accused President Aleksandar Vucic of destabilizing Kosovo.
"Illegal Serb structures transformed into criminal gangs have assaulted Kosovo police, KFOR (peacekeeping) officers, and journalists. Osmani tweeted that those who carry out Vucic's orders to destabilize northern Kosovo must face justice.
Vucic accused Albin Kurti, the prime minister of Kosovo, of fostering tensions. He urged Serbs in Kosovo to avoid conflict with NATO troops.
The United States and its allies rebuked Pristina on Friday after ethnic Albanian mayors assumed office in northern Kosovo's Serb majority area following elections that the Serbs boycotted.
In Zvecan, one of the towns, Kosovo police - staffed by ethnic Albanians after Serbs deserted the force last year - sprayed pepper gas to repel a crowd of Serbs who breached a security barricade and attempted to force their way into the municipal building, according to witnesses.
NATO soldiers in Zvecan were pelted with tear gas and stun grenades by Serb demonstrators. In Zvecan, Serbs clashed with police and sprayed the letter "Z" on NATO vehicles, referencing a Russian symbol used in the Ukraine conflict.
In Leposavic, close to the Serbian border, U.S. peacekeeping troops in riot gear surrounded the town hall with barbed wire to defend it from hundreds of enraged Serbs.
Later in the day, protestors threw eggs at the parked car of the new mayor of Leposavic.
The commander-in-chief of the Serbian armed forces, Vucic, has elevated the army's combat readiness to the highest level, according to Defence Minister Milos Vucevic.
"This suggests that before 2:00 p.m. (1200 GMT), the Chief of the Serbian Armed Forces General Staff issued additional orders for the deployment of the army's units in specific, designated positions," Vucevic stated without further explanation.
According to witnesses, NATO peacekeepers also barricaded the Zubin Potok town hall to safeguard it from irate local Serbs.
Igor Simic, the deputy leader of the Serb List, the largest Kosovo Serb party sponsored by Belgrade, accused Albin Kurti, the prime minister of Kosovo, of stoking tensions in the north.
"Peace is in our best interest. Simic told reporters in Zvecan that the local Albanians are interested in peace, whereas only Kurti seeks to create disorder.
More than twenty years after the Kosovo Albanian uprising against repressive Serbian rule, most Serbs in northern Kosovo have never recognized Kosovo's 2008 declaration of independence from Serbia and still consider Belgrade their capital.
More than 90 percent of ethnic Albanians populate Kosovo as a whole, but northern Serbs have long demanded the implementation of a 2013 agreement mediated by the EU to form an association of autonomous municipalities in their region.
Serbs refused to participate in the April local elections, and ethnic Albanians gained the mayoralties in four Serb-majority municipalities, including North Mitrovica, where no incidents were reported on Monday.
Serbs demand that the Kosovo government remove ethnic Albanian mayors from town halls and permit Belgrade-funded local administrations to recommence operations.
Three of the four ethnic Albanian mayors were escorted into their offices on Friday by police, who were pelted with rocks and responded with tear gas and a water cannon to disperse the demonstrators.
The United States and its allies, who have fiercely supported Kosovo's independence, reprimanded Pristina on Friday, stating that the imposition of mayors without popular support in Serb-majority areas undermines efforts to normalize relations.
Following a weekend phone call with the EU's foreign policy chief, Kurti defended Pristina's position by tweeting that he "emphasized that elected mayors will provide services to all citizens."
Foreign Minister of Serbia Ivica Dacic told RTS that having non-Serb mayors in municipalities with a majority Serb population is impossible.
After meeting with Kurti, U.S. Ambassador to Kosovo Jeffrey Hovenier told reporters, "We are concerned about reports of violence today against official property."
"We've seen pictures of graffiti on KFOR and police vehicles, and we've heard reports of attacks on journalists; we condemn these actions; this is not an appropriate response."