The international war crimes tribunal in The Hague has reversed its conviction of three Bosnian Croats, whom it had sentenced to jail for taking part in a massacre of more than 100 Muslims in 1993. The tribunal's appeals chamber criticized prosecutors in the original trial for building a weak case, based on unreliable witnesses, and said judges failed to sufficiently assess the evidence against the three.

Brothers Zoran and Mirjan Kupreskic, and their cousin, Vlatko Kupreskic, have been ordered released from the jail in The Hague where they have spent the past four years.

The three Bosnian Croats had been sentenced to terms ranging from six to ten years for taking part in the ethnic cleansing of Muslims in the village of Ahmici in central Bosnia eight and a half years ago.

The appellate court says the case against them was flawed from the beginning, with prosecutors relying on vague indictments and questionable testimony from witnesses. It also says the trial court did not address discrepancies between witness statements, and had conducted what it calls a critically flawed assessment of the evidence against the three men.

The appeals chamber also reduced the sentences of two other Bosnian Croats convicted in the case. Vladimir Santic, originally sentenced to 25 years in jail, had his sentence reduced to 18 years. And Drago Josipovic's 15 year sentence was cut to 12 years. The overturning of the three Kupreskics' sentences was the most sweeping ruling yet by the tribunal's appeals chamber. It is a severe blow to the court's chief prosecutor, Carla del Ponte, who is currently in Yugoslavia pressing the governments of Serbia and Montenegro to surrender more war crimes suspects.

Ms. del Ponte says the Yugoslavs have failed to cooperate with the court since the Serbian government handed over former Yugoslav President Slobodan Milosevic last June.

The federal Yugoslav government has long maintained that the tribunal is biased against Serbs. Several of the dozen or so suspects Ms. del Ponte wants extradited enjoy immunity from any criminal procedure. One of them is Serbian President Milan Milutinovic. At least three others are members of Parliament.