UNITED NATIONS (AP) _ The U.N. Security Council said Friday extremist violence in Macedonia threatens the stability and security of the Balkans.

In a statement after an open debate on Kosovo, the council backed efforts by the Macedonian government to cooperate with NATO and other international organizations to end the violence that started a month ago.

Macedonia demanded at the council meeting that the United Nations and NATO-led peacekeepers in Kosovo halt the infiltration of ethnic Albanian extremists and destroy their bases on the border.

``What we are witnessing, in effect, is an armed aggression from abroad, from Kosovo,'' Macedonia's U.N. Ambassador Naste Calovski told the council. ``It is urgent that the extremists are isolated and unable to proceed with their agenda and terrorist activities.''

The council issued a statement last week condemning the attacks in Macedonia. The statement agreed on Friday by all 15 council members went further, strongly condemning ``the continuing extremist violence'' and saying it ``constitutes a threat to the stability and security of the entire region.''

The council made no direct reference to Kosovo, but at Macedonia's request it added a phrase saying the violence was ``supported from outside the country.''

The council also said it remains concerned about the security situation in southern Serbia bordering Kosovo ``as a result of the violent actions of ethnic Albanian armed groups.''

The insurgents insist that the majority of their fighters are ethnic Albanians from Macedonia, many from the border region in the north of the country.

Their demands include an internationally supervised census to determine the size of the ethnic Albanian community in Macedonia and constitutional changes to increase their political and economic influence.

Kosovo is a province of Serbia, the dominant of Yugoslavia's two republics.

The United Nations took charge of administering and rebuilding Kosovo in June 1999 after a 78-day NATO bombing campaign forced Yugoslav troops to withdraw and ended then-President Slobodan Milosevic's attacks against independence-minded ethnic Albanians.