The UN refugee agency has voiced concern over what it says is pressure by Iran on Afghan refugees in the country to return home.

The UNHCR warns that premature, forced or induced returns at this time will not be sustainable

UNHCR's Maki Shinohara

"The UNHCR is alarmed at the sudden increase in the number of [people] returning from Iran, which we believe is the result of pressure by the authorities," UNHCR spokeswoman Maki Shinohara said.

She said the number of Afghans crossing the border from Iran had risen from a weekly average of 6,500 in July to 10,000 in the first week of August.

Iran has denied putting pressure on the refugees to leave.

Some one and a half million Afghan refugees are estimated to live in Iran, having fled years of civil war and natural disaster in their country.

Later this week, the Iranian President Mohammad Khatami is due to visit Kabul - the first by an Iranian head of state since the overthrow of the Taleban last year.

Concerns raised

Ms Shinohara said that part of the problem was that the Iranian authorities were telling the refugees that unless they returned to Afghanistan immediately, they would not be eligible for UN financial assistance.

The UN has warned against forced repatriation

This was untrue, said Ms Shinohara.

She said the UNHCR had raised its concerns several times with Iran.

"The UNHCR warns that premature, forced or induced returns at this time will not be sustainable and may lead to a reversal of the movement in the future," Ms Shinohara said.

A voluntary repatriation programme for Afghan refugees was launched in March.

Voluntary return

The vast majority of returnees have been from Pakistan

At the start of the programme tens of thousands left each week, leading to concern that the infrastructure in Afghanistan was not sufficient to cope with such numbers.

But only 116,000 of the Afghan refugees in Iran have returned so far, according to UN figures.

However, the Iranian authorities have denied charges that they are putting pressure on them to leave or deporting them.

The issue is expected to figure prominently in talks between President Khatami and Afghan leaders, along with security issues and drug trafficking.