Updated

Kosovo police arrested three ethnic Serbs, including two police officers, early Friday on suspicion of involvement in the killing 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 (25 miles) north of the capital, Pristina, as suspects in the January slaying of Oliver Ivanovic, police said in a statement. A fourth Serb was arrested for resisting police. A fifth person is still at large, police said.

Police said they seized evidence for the investigation into Ivanovic's killing during raids in four locations.

A prosecutors' statement said they had found illegal weapons and other material.

The arrests triggered protests by ethnic Serbs on Mitrovica's main square.

Prime Minister Ramush Haradinaj's Cabinet issued a statement calling for calm and saying that the police operation was not linked to any political development.

"I assure all citizens of the Kosovo state and the public order institutions that it (the police operation) will be never be oriented against any ethnic or political grouping," Haradinaj wrote on his Facebook page.

Earlier this week, tensions soared after Kosovo failed to become a member of the international police organization, Interpol, following intense lobbying by Serbia. Kosovo slapped a 100 percent tax on goods imported from Serbia in an apparent retaliation.

Ethnic Serb leaders in Kosovo also called for calm and also to Serbia and international community to assist them.

Goran Rakic, mayor of Northern Mitrovica, told Associated Press television they had formed a crisis center and called on the international community and Serbia for help. He said he had talked on phone with Serbian President Aleksandar Vucic.

Igor Simic, an ethnic Serb lawmaker in Kosovo, criticized police "excessive force" during the arrests.

The Serbian government is to hold an emergency session to discuss the crisis. Serbian President Aleksandar Vucic has called a meeting with the commanders of army and police and security services.

Kosovo's ethnic Albanians fought a bloody war with Serbia in 1998-1999 which ended with a 78-day NATO air campaign in June 1999.

Kosovo declared independence from Belgrade in 2008 which Belgrade still refuses to recognize.

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Dusan Stojanovic and Jovana Gec contributed from Belgrade, Serbia.