Refugee officials say as many as 25,000 civilians, driven from their homes in southwestern Kosovo, are desperately trying to escape a pincer strike by Serb troops and tanks that blasted their villages.

The latest victims of the crackdown on ethnic Albanians in the Serbian province fled on tractors and wagons heaped with their belongings, clogging a dirt road Wednesday in a column seven miles long, according to Western observers who visited the area.In a news release Wednesday, the Geneva-based United Nations High Commissioner for Refugees warned it "fears slaughter may occur if a shell hits the column of people."

Kosovo is in southern Serbia, the dominant of two republics left in the Yugoslav Federation. Its population is 90 percent ethnic Albanian, most of whom back the rebels' armed struggle for independence after decades of repression by Serbian authorities.

One official said the current refugee situation threatens to create as many as 25 new ghost towns in Kosovo, where dozens of villages already have been charred and emptied in the face of shelling or clashes between Serb security forces and ethnic Albanian rebels.

Fernando del Mundo, a UNHCR spokesman, described a chaotic exodus that apparently began Tuesday from villages in an area about 18 miles south of Pec, Kosovo's second-largest city.

"They're panicking and going everywhere, but they don't know which way to go," said del Mundo, who heard shelling and saw billows of smoke in the area Wednesday. "The shelling is closing in like a pincer."

Tens of thousands of others remain dangerously close to the shelling and may also soon flee, he said, swelling the number of Kosovo refugees from its current estimate of 265,000.

Western officials fear the worst if urgent help isn't provided for the 50,000 or so refugees now living in the hills and forests and facing starvation or freezing.

"If something isn't done soon, we can expect a humanitarian drama within weeks," Belgian Foreign Minister Erik Derycke said in Pristina after meeting with ethnic Albanian leader Ibrahim Rugova.

The United Nations estimated this week that 600 to 700 civilians have been killed in six months of fighting between Serb-led forces and Kosovo Albanian rebels.

While world leaders have condemned the Serbs for killing civilians and for their scorched-earth tactics targeting ethnic Albanian villages, the Serbs also accuse the militants of massacring Serb civilians.

Western officials have held out the threat of military intervention for months if Yugoslav President Slobodan Milosevic doesn't halt the offensive. But such plans have been stymied by the failure to reach an international consensus and by the difficulties of mounting an effective military action in the mountainous region.