Yesterday's violence in Kosovo, in which dozens of international peacekeepers were injured in the northern town of Mitrovica, raises the fear of fresh fighting in the Balkans, may put new demands on Britain's overstretched peacekeeping forces and heightens tensions between the West and Russia. It is the worst violence since the anti-Serb riots exactly four years ago that killed 19 people and left hundreds of Serb churches and homes burnt out. The battle by Serbs occupying the courthouse in the divided city against United Nations police, backed by Nato troops, came a month after Kosovo's unilateral declaration of independence and was intended to mark the refusal of the 120,000-strong Serb minority to accept separation from Serbia. The violence has punctured European hopes that the crisis over independence had passed, threatens to provoke further riots in northern Kosovo and brings closer the prospect of ethnic partition for the territory.

The declaration of independence by the Albanian-dominated parliament in Pristina has already destabilised the governments in two neighbouring countries. In Belgrade, Vojislav Kostunica, the Prime Minister, led his nationalist party out of coalition government in protest at the EU's recognition of Kosovo and Serbia's negotiations on closer association with Brussels. And in the Republic of Macedonia the Albanian minority has also quit the coalition, saying it would not return until Macedonia recognised Kosovo's independence. Russia called the violence a direct result of the “illegitimate” declaration and insisted yesterday that the West return to more talks.

Russia's demand will not be met. Most of the EU is now committed to Kosovan independence. It is preparing to send a 2,000-strong police and justice mission to take over from the UN administration. But the EU faces a dilemma. It does not want its largest civilian aid programme to heighten opposition within Serbia to President Tadic, who favours continued talks with Brussels and who has called a general election on May 11. Russia, meanwhile, is courting the anti-EU nationalists, with the offer of a new gas contract.

Brussels has so far shown little of the same robustness. Its woolly call for restraint, issued yesterday, said the EU was “very concerned” about the tense situation, and insisted that all parties should build a multi-ethnic Kosovo based on the rule of law. That will cut little ice - in Belgrade, Pristina or on the barricades in Mitrovica. Brussels must offer the Serbs a real choice: between a tough military response, if Belgrade incites more demonstrations; and a generous package making emergency aid available to Serbia's stuttering economy if Belgrade tries to calm passions in the region. Serb voters have to see that it is in their interest to strengthen links with the EU members around them. They must also understand that Russia's manoeuvrings have more to do with Moscow's determination to sabotage Nato expansion on its flanks than offering a way to re-establish Serbia's control over its lost province.

Kosovo's Albanian majority cannot hope to contain Serb anger by the use of force alone. Detaching the Serb north from Kosovo is no answer and would lead to ever-less viable political units. But the Serbs should be offered real political autonomy. If Pristina is to establish a viable state, this must be done with the consent of all, and not in the teeth of riots and bloodshed.