Serb forces have been accused of breaking a ceasefire agreement with an offshoot of the Kosovo Liberation Army seeking to unite three mainly Albanian areas of southern Serbia with Kosovo.
A spokesman for the Liberation Army of Presevo, Medvedja and Bujanovac - known as the U-C-P-M-B - claimed on Monday that Serb forces are breaking a ceasefire agreement between the two sides in southern Serbia.
Speaking to A-P-T-N, Commander Sami Azemi Serb said the U-C-P-M-B would respond "robustly" to continuing Serb advances towards their positions.
He also expressed defiance at threats by Zoran Djindjic - ally of Serb President Kostunica - forcibly to remove the U-C-P-M-B after elections in December.
Yugoslavia's government on Tuesday sought a U-N Security Council meeting on the crisis along a rebel-controlled buffer zone between Kosovo and southern Serbia.
The call came after ethnic Albanian militants in the zone fired at government forces.
Around midnight on Monday, shots were fired at army positions in southern Serbia just outside the buffer zone.
The Serbs did not return fire.
It was the first time militants have fired on the army.
In the second attack early Tuesday, a machine gun was fired at Serbian policemen near Sveti Ilija, also in the buffer zone.
It controls a number of areas within the so called "Ground Safety Zone", a five kilometre (three mile)-wide stretch of land on the Serbian side of the border with Kosovo.
The buffer zone was set up in June 1999 to prevent Yugoslav forces from threatening the NATO-led peacekeeping mission in the southern Serbian province of Kosovo.
Neither the Serb army nor K-FOR is allowed within the zone, which is patrolled by Serb police.
Belgrade has demanded the peacekeepers act more strongly to prevent militants from inside Kosovo from entering the three-mile-wide buffer zone.
Two weeks ago four Serbian policeman were killed and a dozen more injured in fighting with the U-C-P-M-B.
After that a ceasefire was agreed between the two sides which the Albanians claim the Serbs are now breaking.
"The Serbs have broken the so-called ceasefire. They entered the village of Lucan. We held our fire. And now I am telling the Serb police and the MUP (military police) that every step they take towards our position, we will respond robustly."
SUPER CAPTION: Sami Azemi, UCPMB Commander
(Responding to threats by Zoran Djindjic to come and forcibly remove the UCPMB after December elections) "We are not afraid. Ever since the day that we took up arms, we have known who we were going to fight. And no matter what we will stick to our aims until the day we are free."