ROME — The most senior Kosovo Albanian suspect to be prosecuted by the U.N. war crimes tribunal was cleared yesterday of all counts involving the murder and torture of Serb civilians, a verdict that quickly inflamed passions across the Balkans.

The decision to acquit and free Ramush Haradinaj, a former guerrilla commander and prime minister of Kosovo, was met with cheers in the province, but fury in Serbia, where the credibility of the tribunal was immediately assailed.

Kosovo, with American backing, declared independence six weeks ago, a move Serbia adamantly and sometimes violently opposes.

“This is a verdict that strengthens Kosovo,” Mr. Haradinaj said in a statement.

In Pristina, the capital of Kosovo, where Mr. Haradinaj is considered a national hero, cars filled the streets, many adorned with red Albanian flags and their horns blaring in celebration. He is expected to return later today.

Mr. Haradinaj’s tearful wife, Anita, said: “Ramush is coming to an independent Kosovo that he made happen.”

But troubling questions were raised about the efficacy of the trial at the international tribunal at the Hague. Numerous witnesses were too afraid to testify against Mr. Haradinaj and several prosecution witnesses disappeared or died under mysterious circumstances, court officials said.