Serbian Deputy Information Minister Miodrag Popovic said the incident highlighted the fact that Serbs in Kosovo were still at risk four months after the Nato-led K-For troops had moved in to restore order.

"The Dutch forces should have withdrawn and the Russian forces should have been in the Orahovac area, where the ethnic Albanians are keeping their siege for two months now, and the K-for forces don't want to, or there is not the political will, to break the siege," he said.

His comments came as the European Union's senior foreign policy officials arrived in the province to highlight Europe's central role in restoring peace there.

The UN Refugee Agency (UNHCR) said that the attack happened in the western town of Pec when a convoy of about 150 Serbs had been trying to leave the southwestern city of Orahovac for Montenegro.

K-For officials said part of the convoy became detached after a Serb civilian vehicle broke down, and then lagging vehicles stopped to ask directions.

Peacekeepers guard Serbs inside the K-For base

Some of the refugees were dragged from their cars, which were then set on fire, after the convoy was blocked by an angry crowd of about 1,500 Albanians.

Several Serbs fled to a nearby K-For base, which the UNHCR said was then surrounded by the crowd.

At least 18 Serbs were slightly injured in the incident and 19 vehicles set alight, including one owned by the UNHCR.

Volatile situation

The organisation said the incident highlighted just how volatile Kosovo remained.

"It's a very alarming situation when a civilian convoy is attacked and passengers are assaulted in such a way," UNHCR spokesman Peter Kessler said.

"This kind of ethnic violence shows that tensions on the ground here are still extremely high after the ethnic cleansing that occurred."

International aid workers said all the Serbs on the convoy had been checked to make sure they were not wanted in connection with war crimes.

EU visit

During their visit, the EU representatives are hoping to "press home the EU's support for ethnic reconciliation", a spokesman said.

The former Nato chief will press for reconciliation

EU External Relations Commissioner, Chris Patten, and the High Representative for the Common, Foreign and Security Policy, Javier Solana, are due to meet Serb and Albanian leaders, and visit the divided city of Mitrovica.

They are also due to have talks with the K-For commander, General Klaus Reinhardt, and the UN Administrator Bernard Kouchner.

The EU spokesman said the main purpose of the visit was to gain first-hand insights on the "political, security and economic situation in Kosovo, and to visit EU reconstruction assistance projects".