By Susannah Price BBC Islamabad correspondent

The UN refugee agency says more than 25,000 Afghans trying to enter Pakistan have been trapped on the border for months.

Only some of them have shelter

Most of the 6,000 families stranded in deteriorating conditions have been waiting for months for Pakistan to allow them in.

They have been sleeping in the open or in makeshift shelters in the searing heat and dust, although some have now been given tarpaulins.

Aid agencies provide food, water and blankets, but conditions are extremely basic.

The Afghans mainly came from the largest ethnic group, the Pashtuns.

'Persecution'

They said they were being persecuted in the north, where they are in the minority, and that some were being accused of belonging to the Taleban, which had their main support base among Pashtuns.

Others arrived at the desolate waiting area at Chaman because of drought or fighting.

However, Pakistan closed its border and refused to allow them to come in.

The UN refugee agency has just completed a detailed head-count of the Afghans to help aid agencies provide them with necessary relief.

It is looking at the possibility of relocating them to Kandahar Province inside Afghanistan.

At the same time, thousands of Afghans are leaving Pakistan every day to return home.

There were more than 2.5m Afghan refugees in camps in urban areas of Pakistan and now more than a million of these have gone back home.