Three ethnic Serbs, including two police officers, were arrested in Kosovo early on November 23 in connection with the murder of a leading Serb politician in the north of the country.
The three men were arrested in the Serb-dominated town of Mitrovica, 40 kilometers north of the capital, Pristina, as suspects in the killing of Oliver Ivanovic in January, police said in a statement.
A fourth ethnic Serb was arrested for resisting police.
During the raids -- which took place in four locations -- police seized evidence for the investigation into the murder, a prosecutor's statement said, adding that illegal weapons and other material had been found.
The arrests sparked protests by groups of ethnic Serbs on Mitrovica's main square.
The Kosovar government of Prime Minister Ramush Haradinaj called for calm, adding that the operation had no connection to politics.
"I assure all citizens of the Kosovo state and the public order institutions that [the police operation] will be never be oriented against any ethnic or political grouping," Haradinaj wrote on his Facebook page.
Tensions are on the rise after Kosovo failed earlier this week to become a member of the international police organization, Interpol. Meanwhile, Kosovo introduced a 100 percent tax on goods imported from Serbia.
The Serbian government is to hold an emergency session to discuss the crisis, while President Aleksandar Vucic has called a meeting with the commanders of Serbian army, police, and security services.
Ivanovic, a moderate Serb politician, was shot dead in front of his office in northern Mitrovica on January 16.
His killers have never been identified.
He was considered one of a few ethnic Serb politicians capable of building bridges between his community and Kosovo's ethnic Albanian majority.
Russia's Foreign Ministry condemned the arrests of the ethnic Serbs, calling it a "provocation...[in] the Serbian-populated part" of Kosovo.
Russia has refused to recognize Kosovo as an independent country, something that more than 110 other countries around the world have done.
"Pristina's course for ethnic cleansing and unleashing a trade war in the Balkans is apparent," it said in a statement.
