He is making his first overseas visit since taking over as US ambassador to the United Nations.

The BBC's Patrizio Fama reports: "He has been involved with the Balkans since his efforts to bring peace to Bosnia"

Mr Holbrooke, who said he was visiting the region at the request of US Secretary of State Madeleine Albright, is to spend three days in Pristina, on a trip that will also take him to Skopje, Tirana and Sarajevo.

As the visit began, a minister in the Macedonian government was killed when his car was involved in a head-on collision with a vehicle belonging to K-For, the Nato-led peacekeeping force for Kosovo.

Unannounced arrival

Mr Holbrooke's arrival - just three days after being sworn in to his new position - led to media speculation about the reasons behind his visit.

The ambassador is a key figure in Balkan diplomacy, used to mediating between myriad interest groups and political alliances.

Speculation surrounds the Holbrooke visit

Soon after his arrival in Pristina on Saturday, the US envoy drove to the site of three mass graves at Cikatova, west of the Kosovo capital.

There, he was briefed by investigators working for the UN wars crimes tribunal.

"We're here to bear witness," Mr Holbrooke told reporters, as he was shown a ditch from where 50 bodies - believed to have been ethnic Albanians - were exhumed.

Some 129 bodies have so far been recovered from the Cikatova site. But reports say identification has been difficult because the bodies are in an advanced stage of decomposition.

Speculation

There has been no official explanation of the reasons for Mr Holbrooke's visit, but media reports say it is intended to provide him with a detailed view of the situation on the ground.

Nick Thorpe in Pristina: "Mr Holbrooke described his visit as an implementation, not a negotiating trip"

One report speculated that the ambassador was on a fact-finding mission on the US role in the region, including a study of its military presence.

Mr Holbrooke helped broker the 1995 Dayton peace accords which brought the Bosnian war to an end. He was also President Clinton's special envoy to Yugoslavia, charged with negotiating with President Slobodan Yugoslavia.

Minister killed

Radovan Stojkovski, a minister in the Macedonian government, was killed along with his wife and daughter when their car collided with a Norwegian vehicle attached to the Nato-led K-For peacekeeping force on a main road south east of Skopje.

Two Norwegian K-For officers were slightly injured in the accident. A K-For statement expressed deep regret over the accident, and said the Norwegian vehicle appeared to have been travelling in the wrong direction on the carriageway.