The Iranian government says several foreign nationals were among those arrested last week during clashes between opposition protesters and security forces.
Intelligence Minister Heydar Moslehi did not say Monday which countries the detained were from. But during an interview with state television, he accused them of "pursuing propaganda and psychological warfare."
Moslehi said the foreigners were found to be carrying cameras and other equipment.
More than 500 people were arrested on December 27 when opposition supporters staged protests during the Shi'ite holiday of Ashura. Eight people were killed in the clashes that followed.
Conservative clerics have accused opposition supporters of being enemies of god or "mohareb," an offense that carries a death sentence.
The violence was the most serious in Iran since the protests that erupted after June's disputed presidential election, which resulted in the re-election of President Mahmoud Ahmadinejad.
Some information for this report was provided by AP, AFP and Reuters.