BELGRADE (Reuters) - Police in Kosovo have made the first arrests in connection with the murder of Kosovo Serb leader Oliver Ivanovic in January, detaining three suspects including two ex-police officers in a pre-dawn raid on Friday, officials said.

FILE PHOTO: A portrait of Oliver Ivanovic is seen during a memorial service for the Kosovo Serb leader in Mitrovica, Kosovo, January 16, 2018. REUTERS/Djordje Kojadinovic/File Photo

Ivanovic, 64, was shot dead on Jan. 16 as he arrived at his party office in Mitrovica, a town bitterly split between Kosovo’s majority ethnic Albanians and minority nationalist Serbs, who dominate the northern region surrounding Mitrovica.

He had been facing retrial over killings of ethnic Albanians during Kosovo’s 1998-99 guerrilla uprising against repressive Serbian rule. Kosovo gained independence from Serbia in 2008 and Ivanovic subsequently became known as a relative moderate for advocating dialogue and compromise with Kosovo Albanians.

A special police unit sent by the Kosovo Albanian government in Pristina carried out the raid in the Serb-dominated north side of Mitrovica and all three arrested suspects were Serbs, a police statement said. It said a fourth Serb was detained for resisting and hindering the operation.

“Relevant evidence” was collected, it added.

Kosovo’s north, where some 50,000 Serbs live, has been in legal limbo since the 1990s war - politically loyal to Serbia but generally a no-go territory for both Serbian and Kosovo police, with Serb criminal gangs exerting a powerful grip.

Serbia’s government protested at the Kosovo police action. “The ultimate goal of this is intimidation of all Serbs in Kosovo,” said Nikola Selakovic, an aide to President Aleksandar Vucic. “What is the purpose of arresting people at dawn?”

Tensions resurged between Kosovo and Serbia on Wednesday when the Pristina government raised tariffs on Serbian goods from 10 to 100 percent after Belgrade blocked its former province from joining Interpol. Serbs vowed protests at border crossings with Serbia later on Friday.

Kosovo’s independence is recognised by more than 110 nations but not by Serbia, Russia or five EU states. Belgrade and Moscow have blocked Kosovo from joining the United Nations.

In 2013 both countries agreed to an EU-sponsored dialogue to resolve outstanding issues, but little progress has been made.