NATO's South-East Europe commander Admiral Gregory G. Johnson Johnson said the pattern of events would lead one to believe there was a "modicum of organization."

"Those who are responsible for that bear a great burden because they have just created a very bleak day in the history of Kosovo and more importantly a bleak day in the future of Kosovo," Johnson told journalists in the capital Pristina after meeting top UN official in Kosovo Harri Holkeri and local leaders.

Johnson said the rioting and clashes between the majority Albanians and minority Serbs were acts of "simple crime."

"What we have here is common criminal behaviour, thuggery. There's nothing nice about it, there's nothing courageous about it and there's nothing patriotic about it. It's simple crime," he said.

Some 17,000 troops - known as KFOR - stationed in Kosovo are under the command of NATO and are responsible for securing the province.

Johnson however brushed aside the possibility the troops were not up to the challenge.

"If we had 50,000 troops here, with the things that have happened over the last day we would not be able to defend every piece of every building and every citizen here," he said.

Johnson arrived in Kosovo's capital Pristina just ahead of the advance party of some 1,000 NATO reinforcements that are to be sent to the troubled province to contain the clashes between Serbs and Albanians that have so far left 22 dead and over 500 injured.

The province saw the worst ethnic violence since it came under UN and NATO control in 1999 as Serbs and Albanians clashed in virtually every major centre in Kosovo.

Scores of Serb houses have been torched and dozens of Orthodox churches set ablaze.

On Thursday afternoon UN police in riot gear supported by armoured vehicles fired tear gas at several thousand Albanians outside Pristina in an attempt to prevent them from reaching Serb villages just south of the capital.

It is feared the violence could have dealt a lethal blolw to UN's stated goal of building a multiethnic Kosovo, as newly built houses belonging to Serbs returning to the province were levelled in several places.

"We have many difficulties in introducing the goal of a multiethnic Kosovo," Holkeri told journalists after meeting Johnson and Kosovo's leaders.

"I have understood that Kosovo is a home for tens of thousands of Serbs. That is why my answer is that people must be allowed to stay at home," he said.

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