Northern Kosovo was hit by fresh violence on Tuesday after police arrested Kosovo Serb Milun ‘Lune’ Milenkovic on suspicion of orchestrating attacks against NATO peacekeepers at the end of May, testing international efforts to de-escalate tensions.

Dozens of peacekeepers and Serb civilians were injured in clashes at the end of May during protests over the installation of an ethnic Albanian as mayor of the predominantly Serb-populated municipality of Zvecan following local elections boycotted by Serbs.

Local media reported that police used tear gas during the arrest of Milenkovic in a hair salon on the northern, mainly Serb side of the ethnically divided town of Mitrovica.

Sirens blared and dozens of residents gathered outside a local school.

Kosovo Interior Minister Xhelal Svecla confirmed the arrest on Facebook, describing Milenkovic as a leader of the Civil Protection organisation, a group that should have been integrated into Kosovo’s public institutions under a 2015 European Union-mediated agreement between Serbia and its former southern province.

“During his arrest, three Kosovo police officer sustained minor injuries,” Svecla wrote, accusing Milenkovic of heading “gangs that have terrorised citizens” for years.

The arrest came as Kosovo Prime Minister Albin Kurti confirmed he had presented to EU foreign policy chief Josep Borrell a five-point plan for de-escalation in northern Kosovo, which includes new municipal elections.

But the Serbian government’s pointman for Kosovo, Petar Petkovic, said the arrest showed Kurti is “only interested in conflicts and war in the north”.

Petkovic said Milenkovic was “no criminal” and that his arrest took the form of a “siege” with tear gas tossed indiscriminately at residents.

According to local news portal KosSev, those gathered chanted ‘Betrayal’ and slogans against Serbian President Aleksandar Vucic.