Iran says several foreign citizens were arrested during clashes between opposition supporters and security forces last month.
Intelligence Minister Heidar Moslehi told state television that the foreigners entered Iran two days before the Ashura religious festival, which fell on December 27, and that they were "leading a psychological war against the system."
He did not elaborate on how many were arrested or their nationality.
Officials so far only confirmed the arrest of one foreign citizen, a Syrian journalist working for Dubai TV.
At least eight people died and hundreds were arrested during the protests, the worst unrest in months between opposition supporters and security forces.
Separately, a pro-reform website said 88 Tehran University professors appealed in a letter to Iran's supreme leader, Ayatollah Ali Khamenei, to stop violence against opposition protesters.
with agency reports