THE HAGUE, Netherlands- The chief prosecutor of the United Nations war crimes tribunal has formally appealed the acquittal of former Kosovo Prime Minister Ramush Haradinaj.

The chief prosecutor said widespread intimidation and fear prevented key witnesses from fully testifying in the trial.

The appeal at the Yugoslav war crimes tribunal comes just days after two former top Kosovo government officials pleaded not guilty to charges of trying to dissuade a witness from appearing at Ramush Haradinaj's trial.

Haradinaj, a former commander of the rebel Kosovo Liberation Army during the 1998-99 conflict with Serbia, was acquitted last month of responsibility for murder, rape and torture committed by his troops.

In their appeal, the prosecutors alleged that widespread intimidation of witnesses prevented them presenting all their evidence. They demanded a retrial on six of the 37 charges Haradinaj, Idriz Balaj and Lahi Brahimaj faced.

A retrial would be unprecedented at the Yugoslav tribunal, court spokeswoman Nerma Jelacic said. The tribunal was created in 1993 to prosecute those most responsible for atrocities during the Balkan wars that started two years earlier.

Nearly every judgment or sentence has been appealed by one side or the other, or both.

Prosecutors called 81 witnesses during the 113-day trial, but several other key witnesses refused to testify or only took the stand after being indicted for contempt of court. The court guaranteed anonymity to 34 witnesses, but still had to subpoena 18 of them.

Lawyers for the three men did not call any witnesses to testify in their defense, saying the prosecution evidence was so weak their clients did not have a case to answer.

Haradinaj is already back in Kosovo and seeking to resume his political career.

A key ally of the West in the aftermath of the Kosovo conflict, Haradinaj was prime minister for just 100 days before resigning in March 2005 after learning of his indictment.

The appeal says the three-judge trial panel "denied the prosecution a fair trial by not granting it the additional time necessary to exhaust all reasonable steps to obtain the testimony of witnesses."

If the prosecution had called all its witnesses, the defense may have countered with their own witnesses, the appeal document said. Therefore, it would be inadequate for an appellate court to merely overturn the acquittals, and a new trial should be held, it said.

The court is under pressure from the U.N. Security Council, which funds the it, to conclude all trials by 2010.

In their 277-page judgment issued April 3, trial judges said they "gained the strong impression that the trial was being held in an atmosphere where witnesses felt unsafe."

But it also said much of the prosecution's evidence was "vague, inconclusive or nonexistent."

Last Tuesday, a former minister in Haradinaj's government and his deputy appeared at the Hague-based court to face charges of contempt of court for the alleged attempted intimidation of a witness.

Astrit Haraqija, the former minister of culture, youth and sport, is accused by the Yugoslav war crimes tribunal of sending his aide Bajrush Morina to dissuade a witness from giving evidence. Despite the pressure, the witness did testify, prosecutors said.

Prosecutors also appealed Balaj's acquittal on three charges of murder, rape and torture.