But as the number of Afghans there has grown, Iran has made it nearly impossible for them to claim the refugee status that would give them international legal rights and access to aid, medical care and education.

“Iran is deporting thousands of Afghans to a country where the danger is both real and serious,” said Joe Stork, deputy director for the Middle East and North Africa at Human Rights Watch, as the group’s 124-page report was released. “Iran has an obligation to hear these people’s refugee claims rather than sweeping them up and tossing them over the border to Afghanistan.”

The report expressed particular concern about the conditions for Afghan children, many of whom sneaked alone into Iran, seeking work for their families at home. In many cases, Afghan children discovered on the street have been arrested by the Iranian authorities and summarily deported, separating them from families who may have been in the country for years.

Like other deportees, such children are expected to pay for their transport to the border, and for food while they are in detention and transit centers. Those who cannot are often beaten and starved, according to interviews cited in the report.

“Afghan migrant children in Iran can be arrested at virtually any time, with little or no access to legal due process or the protections guaranteed children under international law,” the report said.

Over all, Human Rights Watch said, as many as 1,500 people a day are deported across Iran’s two official border crossings with Afghanistan — particularly the crossing at Islam Qala, a sandy town on the main highway to the city of Herat in western Afghanistan.

Afghan refugees are forcibly repatriated six days a week. They arrive on foot, by bus and in taxis. Some have suitcases filled with years of belongings; others have only the clothes on their backs. When asked, most say they were deported because of improper paperwork.