Kosovo Serbs sacked border posts in the newly independent republic on Tuesday, to warn they won't let a new frontier separate Serb from Serb, whatever Kosovo's Albanian leaders and their Western backers say.
Mobs of several hundred men, some masked, torched UN, customs and police offices housed in containers at two border posts on the boundary line between Kosovo and Serbia.
No casualties were reported but the crossings were temporarily closed. "It seems well organised, according to the number of buses we saw moving to the north," said a spokesman for the Nato-led peacekeeping mission KFOR, whose troops were called in by Kosovo's United Nations administrative mission, UNMIK.
Nato troops went in to back up local police and restore order. Until 1999, this was an unmarked Serbian provincial border. Until last week, it was a UN-supervised crossing. But with Kosovo's declaration of independence on Sunday, it became an international frontier, at least for states recognising Kosovo.
A Serb journalist told the BBC the attacks were triggered by rumours Kosovo's new flag was about to be raised at the posts. Kosovo Serbs, backed by the Serbian government and its ally Russia, have warned that they will not recognise the authority of a European Union law-enforcement mission due to assume supervision of Kosovo from UNMIK over the next four months.
Serbia, which has been hoping to move closer to the EU, has recalled its ambassadors to Washington, Paris and some other countries in protest at recognition of Kosovo but insisted it was not cutting ties.
"We do not intend to find ourselves in self-imposed isolation," Beta news agency quoted the ambassador to Moscow, Stanimir Vukicevic, as saying. Serbian state institutions are well entrenched in the enclave, now with explicit Russian diplomatic backing. "We'll strongly warn against any attempts at repressive measures should Serbs in Kosovo decide not to comply with this unilateral proclamation of independence," Russia's UN ambassador Vitaly Churkin said on Sunday.