BELGRADE, Serbia —  Serbian officials said Friday the war crimes acquittal of a former Kosovo rebel leader will increase tensions in Kosovo and diminish the chances that top Serb fugitives Ratko Mladic and Radovan Karadzic will be arrested.

The U.N. tribunal in The Hague, Netherlands, ruled on Thursday that there was not enough evidence to convict former Kosovo Prime Minister Ramush Haradinaj of murder, torture and rape of Serbs and non-Albanians during the Kosovo war.

The crimes were committed by his rebel Kosovo Liberation Army soldiers. Haradinaj was exonerated of responsibility and of a conspiracy to drive ethnic Serbs from Kosovo to seize complete control for ethnic Albanians.

The judges said much of the evidence was "vague, inconclusive or nonexistent," but they also acknowledged that many witnesses were too afraid to testify, even when the court indicted them for contempt. The prosecution had not yet decided whether to appeal.

Haradinaj was released from a U.N. jail and was to return to Kosovo on Friday.

Kosovo declared independence from Serbia on Feb. 17. Belgrade says the action violated international law and has pledged to retake the territory one day.

In Serbia, pro-Western and nationalist politicians joined law experts in condemning the ruling, saying there had been sufficient evidence to convict Haradinaj, who was one of the most feared rebel leaders of Kosovo's 1998-99 war.

"The ruling is truly worrisome," Prime Minister Vojislav Kostunica said late Thursday on local Pink television. "It turns out that crime pays."

Kostunica's minister for Kosovo, Slobodan Samardzic, said: "The ruling is catastrophic and will have numerous political, moral and legal consequences."

Hardline nationalists cited Haradinaj's release to demand that Serbia halt any cooperation with the Netherlands-based court.

Some officials said the chances that Serbia will now hand over the two most wanted Bosnian Serb fugitives _ Karadzic, the wartime political leader, and Mladic, his military commander _ are now minimal because no Serbian government could make such a move against the two, who are still widely regarded as national heroes here.

"Unfortunately, after this, Radovan Karadzic and Ratko Mladic will never end up in the Hague," said Oliver Ivanovic, a moderate Serb leader from Kosovo.

Karadzic and Mladic are both wanted on genocide charges for orchestrating the 1995 massacre of 8,000 Muslims in Srebrenica and other war crimes during the 1992-95 Bosnian war. The two remain at large, despite huge international pressure on Serbia to arrest them.

Serbia's pro-Western leaders have in the past pledged to capture the two. But they also criticized Haradinaj's acquittal and are considered unlikely to seek the arrest of the Serb fugitives before parliamentary elections in May, during which the reformists will face a tough challenge from the nationalists.

Pro-Western Serbian President Boris Tadic said that Haradinaj's acquittal "does not bring justice and does not encourage the Serbs and other non-Albanians to trust they will have a safe and calm life in Kosovo in the future."

Deputy Prime Minister Bozidar Djelic added that "Hardinaj's acquittal presents a huge blow to stability in the region and will have negative effect on the reconciliation process."

Serbia's war crimes prosecutor, Vladimir Vukcevic, said that the acquittal is so "outrageous" that the U.N. war crimes tribunal for former Yugoslavia "is ready for retirement."

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