The visitors were Serbs from outside Serbia and other Slavs, including Russians. They came, it is alleged, at the invitation of Serbian paramilitaries to take part in atrocities against the province's Albanian population. One of the reasons for using them, it is claimed, was to ensure that the perpetrators would be difficult to track or indict.
The allegations have come from several areas, in particular Glogovac, west of Pristina. Here local people say they have details of the paramilitary units serving there. Russians, Bulgarians and Serbs from western Europe were in their ranks. Russian soldiers now in Kosovo also speak of compatriots who had done short tours in Kosovo.
If the reports of foreign mercenaries are true, the task facing war crimes and human rights investigators is even more complex than first imagined. The extent of the crimes is already turning out to be far greater and more grotesque than previously thought. The statement of the Foreign Office minister Geoff Hoon, that the number of murder victims could be 10,000 slaughtered in 100 separate massacres, may have been a conservative estimate. Robin Cook, the Foreign Secretary, did not mince his words yesterday. "The scale of systematic butchery we have found is profoundly shocking," he said.
As the Yugoslav forces move out of Kosovo, teams from the International War Crimes Tribunal in The Hague are moving in, spearheaded by a 15-strong British team which yesterday began digging at Velika Krusa, one of the massacre sites listed in President Milosevic's indictment. The discovery of 100 bodies here appears to bear out the reports gathered from eye witnesses by groups such as Human Rights Watch months ago.
Investigators have already amassed a sizeable volume of information and detailed allegations from Kosovan Albanian refugees, but turning it into evidence sustainable for future prosecution is going to need a high degree of specialised and technical expertise.
Between 350 and 400 investigators will be seconded from a number of countries to add to the tribunal's permanent staff, including some from Scotland Yard and the FBI. The tribunal and its chief prosecutor, Louise Arbour, have been promised the full help of Nato's peacekeeping force, K-For, but with just over 50,000 troops in the province having to cope with the retreating Serbs, the Kosovo Liberation Army and the rebuilding of the shattered infrastructure, resources are thin on the ground.
Ideally the tribunal would like to get a major part of its work done before the deluge of 800,000 refugees bursts back into Kosovo from Macedonia and Albania, and before crucial evidence becomes contaminated. But Paul Risley, a tribunal spokesman, appreciates there will be "enormous pressure to see the loved ones and bury the ones who died in proper graves". The discovery of so many new sites is adding to the pressure.
The investigators will concentrate initially on seven sites originally listed in the war crime indictment papers issued by The Hague, and expand from there.
The first task is to gather and sift through the testimony of witnesses. This is already under way. Next will come the technical study of sites to back up the statements. This is where the skills of the forensic experts will be needed most. Like police and pathologists at the scene of any crime, they will carry out an initial mapping of each site and then take photographs, both videos and stills. Then they will comb through the soil in the hope of detecting telltale blood stains, discarded clothing, shell casings and other weaponry.
Surveillance photos taken by Nato aircraft during their missions over Kosovo will also be minutely examined and the areas featured then visited by investigators. Local people, returning refugees and those internally displaced will be exhaustively interviewed.
A key part of the investigative jigsaw will be to chart the movement of Serbian forces, army, paramilitary and police. Pinning them to locations where alleged atrocities have been committed would open up the avenues to pursue individuals.
The trail to killings and other atrocities can go back a long way. "Lots of our sites are not near graves per se but they can offer evidence of additional war crimes, like the villages targeted and the detention of non-combatants," says Mr Risley. "Checks on border-control stations, for example, have led to evidence of forced expulsions and identity cards being torn up."
Former local employees of international agencies who stayed behind in Kosovo after Nato air strikes began have been keeping records of what occurred. At Podujevo, for example, Veton Bekteshi, a former local representative of the Organisation for Security and Co-operation in Europe, has recorded precise details of abuse by Serbian forces. He has knowledge of several sites of mass graves in the area.
"I have been hiding in the hills for the last three months," Mr Bekteshi said, "but I have been hearing what has been going on. Now that the Serbs have gone I shall try to give what information I have to the investigators."
But the obstacles that lie in the way of bringing those who perpetrated atrocities to stand trial in The Hague are immense. Much anxiety surrounds the role of the Kosovo Liberation Army. Investigators know that the temptation to seek retribution and mete out summary justice is great.
Much evidence has been destroyed by retreating Yugoslav forces. Almost every station of the notorious special police force, the MUP, has seen smouldering piles of ashes of documentation burnt. There have even been reports of the Serbs exhuming dead bodies and incinerating them. However, Western police forces have promised the latest technology they have to address such problems.
"It is not going to be easy, it is going to be extremely time consuming," says Paul Risley. "But we have the ability and the commitment to bring those responsible for these horrific crimes before an international court of law."Reuse content