Iranian state radio quoting the police said the arrests were made when demonstrators and security forces clashed on Saturday around the capital's Azadi square.
The clashes resulted in the deaths of 10 people also, state television said on Sunday.
The opposition led by defeated presidential candidate Mir Hossein Mousavi has remained defiant despite a crackdown by authorities and on Sunday the former premier told his supporters to remain steadfast.
In clear backing for continued demonstrations, he said: "In your protests keep on refraining from violence... I as one of the mourners (of the Saturday killings) invite my dear people to self-restraint. The nation belongs to you."
Iranian state television blamed "terrorists" with firearms and explosives for Saturday's casualties in which 100 people were also wounded, bringing the overall toll reported by state media in a week of violence to at least 17.
Struggling to contain the massive street protests unleashed since the disputed June 12 election, Iranian leaders lashed out at Western nations, foreign media and the exiled opposition.
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