Sofia - A Bulgarian court on Thursday released former Kosovo prime minister Agim Ceku, who was being held on an international war crimes warrant issued by Serbia.

Ceku was arrested Tuesday after entering Bulgaria from Macedonia. Serbia then asked Bulgaria to extradite the former Kosovo premier, but the Bulgarian court ruled for him to be released.

Sofia News Agency reported that Ceku's lawyers presented documents, signed by current Kosovan premier Hashim Tachi, stating that Ceku is a member of Kosovo diplomatic team and thus has diplomatic immunity.

Earlier on Thursday, Thaci told reporters in Pristina that the Kosovan government was working closely with international officials on Ceku's release.

"These are the last efforts of Serbia to harm Kosovo's relations with Bulgaria. Kosovo will soon be a member of Interpol . This is not the first time Serbia has done this, but it will not happen anymore," Thaci said.

It was Ceku's third arrest on the warrant from Serbia, which sentenced him in absentia for the murder of nearly 700 Serbs during the conflict in Kosovo a decade ago.

He was held briefly in Slovenia and Hungary in 2003 and 2004 and was also expelled and banned from entering Colombia last month.

Ceku was the top commander of the Kosovo Albanian insurgent army which fought against Serbia in 1999.

After years of international administration, Kosovo declared unilateral independence from Serbia last February and was recognized by United States and most of the European Union, including Bulgaria. Serbia, alongside Russia, refuses to recognise Kosovo.(dpa)