Afghan officials say Iran is sending home around 5,000 refugees a day, but that Afghanistan lacks the capacity to accommodate the influx.
Tehran says the refugees are residing in Iran illegally.
Afghan Foreign Ministry spokesman Sultan Ahmed Bahin told RFE/RL that Iran's action violates previous arrangements between the two countries.
"After the publishing of the news about the expulsion of our refugees, we sent a note to Iran's embassy and expressed concern," Bahin said. "We said the move goes against talks between Afghan Foreign Minister Dadfar Spanta and Iranian officials, where it was said that patience and tolerance would be used regarding the deportation of refugees."
He added that refugees should be dealt with based on international regulations.
Nearly 2 million Afghan refugees are believed to be living in Iran.
Kabul Mulls Relations Iran
Afghanistan has recently been preoccupied with its relations with Pakistan. But increasingly, ties with Tehran are coming to the fore. more
Between Washington And Tehran
Afghan Foreign Minister Rangin Dadfar Spanta told RFE/RL in May 2006 that his country could help improve relations between Iran and the United States. more