More than 200 people were arrested yesterday while trying to protest in Tehran.
Another 40 people were said to have been detained in the city of Isfahan.
Opposition groups had called for rallies over the reported imprisonment of their leaders - Mir Hossein Mousavi and Mehdi Karroubi.
The two men had been placed under house arrest several weeks ago as authorities cracked down on protests staged in solidarity with the uprisings in Tunisia, Egypt and elsewhere.
Their families say that on Monday they were taken to prison, although the government denies this.
There is a growing fever burning up everywhere. Humans of the world are finally realizing who they are and what they deserve. With Egypt and Wisconsin, we the world are moving towards something much different. Gas prices will soon hit their highest and America it's lowest.