Police in Kosovo have arrested four ethnic Serbs in an investigation into the murder of politician Oliver Ivanovic, prompting street protests and complaints from Belgrade as its relations with Pristina continued to fray.

In a dawn raid on Friday, a special police unit detained three people – including two former police officers – for suspected involvement in the killing 10 months ago, and a fourth Serb for allegedly obstructing the operation.

They were held in the mostly Serb half of Mitrovica, the city where Mr Ivanovic was shot dead outside his party’s office on January 16th, triggering an investigation that until now had not delivered any arrests.

Local Serb leaders, backed by Belgrade, accused the government of 90-percent ethnic Albanian Kosovo of trying to intimidate their community, and some Serb-majority areas held protests and blocked roads.

The arrests stoked Serb anger sparked by Kosovo’s imposition this week of a 100 per cent tariff on imports from Serbia, after Belgrade successfully lobbied against Pristina’s bid to join the international police agency Interpol, as part of its opposition to its former province’s 2008 declaration of independence.

‘Full compliance’

“This police operation was in full compliance with the law...I assure all citizens that the state of Kosovo and its law-enforcement bodies will never and in no way be directed against any ethnic or political group,” said Kosovo’s prime minister, Ramush Haradinaj.

The Nato-led peacekeeping operation in Kosovo, known as Kfor, said of the arrests: “There was no unlawful operation or military action, and there has never been any threat to the safety and security of the citizens.”

EU enlargement commissioner Johannes Hahn said he spoke to leaders in Pristina and Belgrade and “agreed on the urgent need for calm and de-escalation, in the interest of the whole region.”

“I offered help to work on rapid, practical solutions for the various trade issues at hand,” he added.

Serbian president Aleksandar Vucic held previously unplanned talks with his military and police chiefs and called a special government meeting.

He also met the ambassadors to Belgrade from Russia and China, which do not recognise Kosovo’s independence.

‘Under threat’

According to Serbian media, he told Moscow’s envoy that this was “the strongest attempt yet to endanger the survival of Serbs in Kosovo”, and he thanked Russia for “understanding exactly what is happening in Kosovo and how peace and stability in the entire region are under threat.”

Mr Vucic reportedly assured the Russian ambassador “Serbia will continue to act seriously and responsibly”, but complained “there are no more reasons to trust the Kfor mission or Nato in Kosovo”.

Kosovo’s police sources told local media that another suspect in the murder of Mr Ivanovic is Milan Radoicic, a powerful Serb businessman turned politician, who was not at his home when it was raided on Friday.