Serbian President Boris Tadic said he expected Bulgaria's explanation over the release of the former Kosovo Prime Minister, Agim Ceku, who is wanted for war crimes in Serbia.

"The way Bulgaria has reacted does not contribute to our good relations. I expect to receive explanations from the Bulgarian authorities", Tadic said as quoted by BETA.

On Thursday, the Court in Kyustendil ruled that Ceku should be released but he is not allowed to leave Bulgaria by July 2 which is the deadline for the prosecution to appeal the court's decision.

Ceku, a former rebel commander who was prime minister of Kosovo between 2006 and 2008, is wanted in Serbia for allegedly committing war crimes during the 1998-1999 fighting in Kosovo between ethnic Albanian rebels and Serb government forces.

Ceku was arrested while entering Bulgaria from Macedonia late Tuesday and on the next day Serbia filed an extradition request with the Bulgarian authorities.

Ceku was traveling to Bulgaria at the invitation of the Atlantic Club, a non-governmental organization, to lobby for NATO membership, the club's honorary president and Bulgaria's former Foreign Minister Solomon Pasi said.

Last month Ceku was expelled from Colombia, after Serbia urged his arrest, but later he transited France en route to the Balkans.

He had previously been detained in 2006 in Slovenia and Hungary.