International monitors said it may be part of a systematic offensive by Serb forces. Villagers have fled the shelling.

The latest fighting broke out in Racak, where 40 ethnic Albanians were massacred on Friday. It has spread to neighbouring villages.

Correspondent Jacky Rowland in Pristina: "Villagers are fleeing"

Artillery barrages continued throughout Monday as Serb forces moved into key positions on hills surrounding the southern villages. Small arms fire was also reported.

International monitors said there had been shelling and gunfire at the villages of Petrova and Malopoljce and Urosevac town. Fighting was also reported around Vasiljevo village in central Kosovo.

Serb police units said the operation was to track down members of the Kosovo Liberation Army, which is fighting for independence from Yugoslavia.

Military movements

International monitors have also reported Serb military movements, but no fighting, in the Podujevo area, where there has been a series of clashes over the last month.

Artur Marquadt: "Ongoing operation"

One international observer, Artur Marquadt, said: "It looks like there may be a simultaneous operation to hit three or four villages in the area. We're hoping that everybody is safely out."

Ethnic Albanian guerrillas said they had attacked a Serb patrol near the town of Kosovska Mitrovica, 40km (25 miles) north-west of the Kosovo regional capital, Pristina.

The Serb Media Centre confirmed the attack and said five policemen were wounded.