By Frances Harrison
BBC News, Tehran
Afghans and other foreigners are no longer allowed to live in any cities on Iran's eastern border with Afghanistan and Pakistan, officials say.
Thousands of Afghans are being sent home
The Iranian state-run news agency, Irna, quoted a senior security official saying all cities in Sistan Baluchistan province would be off limits.
Many refugees and illegal migrants live and work in the border provinces, but have now been told to move elsewhere.
Iran has already begun a huge operation to send home illegal Afghan migrants.
The UN says 70,00 have been expelled in the past month.
The operation saw the eastern border city of Zabul virtually emptied of its sizeable Afghan population.
Now the acting commander of the police has told Irna that all cities in Sistan Baluchistan will be off limits for both legal Afghan refugees and illegal migrants - as well as other foreigners.
He said even those legally in the province should move elsewhere and no excuse such as being involved in trade partnerships with Iranians would be accepted.
Those who failed to move, he said, would be rounded up and expelled.
There have already been concerns about the way Iran is sending home so many illegal Afghan workers - the sheer numbers have been difficult for the Afghan authorities to deal with.
And there have been reports of inhumane treatment, such as families being separated in the deportation process.
Now the director-general for the employment of foreign nationals has told Irna that Iranians who employ illegal Afghans will have court cases filed against them.
He says more than 100,000 illegal Afghans have been sent home in the past month and he predicted that half a million would be returned by September and a million by next March.