MITROVICA, Kosovo (AP) — An international court on Thursday sentenced a leading Kosovo Serb politician to nine years in prison for war crimes against ethnic Albanian civilians — a ruling that could heighten tensions in the Balkan region and prompted Belgrade to start reconsidering its EU-mediated reconciliation talks with Pristina.

Judges of the European Union's justice mission in Kosovo found Oliver Ivanovic guilty of murder and torture of civilians in 1999 during Kosovo's war for independence from Serbia when Serb paramilitary forces attacked ethnic Albanians amid NATO bombings. The alliance launched an air war to stop a bloody Serbian crackdown against Kosovo Albanian separatists.

Judges said Ivanovic was a member of a paramilitary group that chased ethnic Albanians from the Serb-controlled part of the northern town of Mitrovica, separated men from women and children, and tortured and killed at least four of them.

"Oliver Ivanovic was aware of the operation of expelling and killing Albanians ... he willingly complied with the plan, knowing that it would result in the killings," the court ruled.

Ivanovic, considered a moderate Kosovo Serb politician, has denied the charges, which he said were politically-motivated. Four other Kosovo Serbs charged together with him were acquitted.

A strong police force guarded the courthouse Thursday during the sentencing in the Serb-controlled northern part of Kosovo.

Kosovo declared independence from Serbia in 2008. Serbia and Kosovo Serbs do not recognize the split.

Serbian officials denounced Thursday's verdict, warning it could re-ignite ethnic tensions in the already volatile region.

"The ruling in no way contributes to the continuation of the process of stability in the Balkans," Serbian Foreign Minister Ivica Dacic said. "Those who stand behind the verdict are certainly not in favor of peace and stability."

Marko Djuric, a member of a Serbian delegation at EU-mediated reconciliation talks with Kosovo Albanians, said the verdict "has nothing to do with law and justice" and was intended to "humiliate the Serbs."

"The red line is crossed," he said. "It is time to reconsider (the talks) and see what to do next."

Ivanovic was arrested in January 2014. He was the first senior Kosovo Serb official detained by the European Union Rule of Law Mission, EULEX, on suspicion of committing war crimes against Kosovo Albanians.