A war crimes court in The Hague jailed two Kosovo former separatist fighters for four and a half years on Wednesday for intimidating witnesses, in its first ever verdict over Kosovo's 1990s independence conflict from Serbia.

Hysni Gucati and Nasim Haradinaj, the head and the deputy head of a group of veterans from the Kosovo Liberation Army (KLA), were convicted of revealing the names of hundreds of witnesses.

The two men branded witnesses "traitors, spies and collaborators" after publicising classified documents leaked from the Netherlands-based Kosovo Specialist Chambers, the court found.

"The message of the accused to these witnesses was: now that everyone knows who you are, no one can protect you," presiding judge Charles Smith said as he handed down the sentences at the high-security court.

"This judgment clearly paints those acts for what they are: criminal and not patriotic."

The time they have already spent in detention since their arrest in Pristina in September 2020 will be deducted from the sentence. They were also fined 100 euros each.

The judgment is the first by the EU-funded Kosovo Specialist Chambers since it was set up in 2016.

The court operates under Kosovo law but is based in the Netherlands to shield witnesses from intimidation in Kosovo, where former KLA commanders have long dominated political life.

It has issued war crimes charges against several senior members of the KLA, an ethnic Albanian guerrilla group that waged a 1998-99 independence struggle against Serbia, including former president Hashim Thaci.

Gucati and Haradinaj, who had denied the charges, listened to the judgment through headphones and stood to be sentenced.

They were found guilty on five counts including intimidating witnesses and violating the secrecy of the court and cleared of one charge of "retaliation".

The Kosovo Specialist Chambers operates under Kosovo law but is based in the Netherlands to shield witnesses from intimidation in Kosovo The Kosovo Specialist Chambers operates under Kosovo law but is based in the Netherlands to shield witnesses from intimidation in Kosovo Photo: ANP via AFP / Eva Plevier

Gucati and Haradinaj were arrested by heavily armed EU police in a raid on the veterans' headquarters Pristina after it said it had received anonymous packages of the court's confidential files.

Judges said the pair revealed details including names of "hundreds" of witnesses during three press conferences between September 7 and 25, 2020. They also handed out the information to journalists and gave interviews, the judges said.

"These acts took place in a climate of witness intimidation," judge Smith said.

"The accused referred to witnesses and potential witnesses using derogatory and threatening language, calling them traitors, spies, collaborators."

Two witnesses were relocated and others were given "emergency risk planning" as a result of their actions, the judge said.

The court is investigating claims that the Kosovo rebels waged a campaign of revenge attacks on Serbs, Roma and ethnic Albanian rivals during and after the war.

Thaci -- the rebels' former political chief -- was accused by prosecutors of being "criminally responsible for nearly 100 murders".

He resigned after being indicted and pleaded not guilty when he appeared in court in November 2020.

Many KLA veterans fiercely oppose the tribunal's mandate, defending their "just" liberation war against Belgrade's oppression of Kosovo's ethnic Albanian population.

The conflict left 13,000 people dead, mainly ethnic Albanians, and saw several top Serbian politicians and generals later jailed for war crimes.

Tensions between Belgrade and Pristina have remained high.

Serbia, as well as its powerful allies China and Russia, still do not recognise Kosovo's 2008 independence declaration, which has been recognised by more than 100 countries.