The United Nations refugee agency, the UNHCR, says that nearly 20,000 Afghan refugees have gathered at the southern Pakistani border post of Chaman.

The agency says there has been an alarming increase in the numbers arriving at the border to be registered as refugees in recent days.

A UNHCR spokesman in Geneva Kris Janowski said that many of the new refugees were Afghan nomads, or Kuchis, who say they have run out of food because of the drought.

Others are Pushtuns from ethnically-mixed areas of northern Afghanistan who say they have been robbed or intimidated on the orders of local commanders there.

The UNHCR spokesman said that many more people have been seen on the road from the southern Afghan city of Kandahar, walking or driving towards the Pakistani border.

From the newsroom of the BBC World Service