Many of them are from the town of Srbica, which has been badly damaged by shelling.

A convoy of UNHCR trucks has delivered food, blankets and medical aid to the central town of Glogovac, where thousands of refugees have gathered.

Jacky Rowland in Pristina: Predictions of a refugee crisis appear to be coming true

And the UNHCR has reported even more refugees on their way to the town, which lies on the fringe of territory held by the rebel Kosovo Liberation Army.

Another four trucks are now on their way to the town to try to meet the rising demand for help.

A feeding operation is also underway in the regional capital of Pristina.

Reporters who managed to leave Pristina despite restrictions on freedom of movement, said villages were still burning near the scene of Saturday's attacks.

Hiding on the hills

United Nations officials say the full extent of the new refugee crisis is only now becoming clear.

The Serbs have set their sights on KLA mountain bases

Thousands of ethnic Albanians fled to the hills on Saturday when Serbian security forces attacked towns and villages and came out of hiding only on Sunday, swelling the numbers of refugees sheltering in the central town of Glogovac.

The refugees - many of them women and children - are from the town of Srbica and surrounding villages.

Refugee workers who have visited Srbica said it was largely deserted.

They said shops and warehouses had been looted and many houses were burning.

Fighting in the mountains

As aid arrived to help the homeless, reports came in of fresh fighting in northern and central Kosovo.

According to the BBC's Jacky Rowland in Pristina, the security forces appear to be focusing their operations on a north-western mountain range, which has so far been an unshakeable stronghold of the KLA.

Serbian military forces are reported to be taking advantage of the international monitors' departure to attack rebel bases.

In recent weeks, Serbian police and army units have dislodged rebels from villages in the footholds of the hills, and now seem to be trying to drive them out of the higher ground.

Security forces say rebel snipers have been firing at police highway patrols and also allege that the rebels placed explosives on a bridge in central Kosovo.

According to international officials, the Serbs are calculating that they can avoid western military intervention provided they keep the violence at "acceptable levels".