Speaking after talks with UN Secretary General Kofi Annan here, Fischer said the international community and in particular the United States and European Union had to work to restore peace to the troubled Serbian province.

"We have to combine all our efforts within the UN but also within NATO and between the US and EU to establish peace again. The violence must be stopped immediately and those who are responsible for the violence must be brought to trial," he said.

But he added: "We should be very careful in overstretching NATO. NATO has limited capabilities and resources."

NATO peacekeepers were on Thursday trying to keep a safe distance between Serbs and Albanians in the UN-administered Serb province, where at least 31 people have been killed in ethnic violence in the past two days.

The alliance sent up to an extra 1,000 troops there on Thursday to help quell the unrest, the worst bloodshed in the province since the 1999 war there.

On the ground the commander of NATO's peacekeepers gave his troops the green light to use force to quash the violence, while the United States, Britain and Italy agreed to dispatch new forces into the UN-run southern Serbian province.

NATO's top decision making body, the North Atlantic Council, expressed confidence that the extra troops added to the 17,000-strong force on the ground could cope with the crisis.

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