Students demonstrated at Tehran University against the government of President Mahmoud Ahmadinejad on Monday, a reformist website reported, more than three months after Iran's disputed presidential election.
The Norooz website said about 1,000 demonstrators carried placards in green, the campaign color of opposition leader Mirhossein Mousavi in the June election, and called for detained students to be freed and the government to resign.
There were also around 50 members of a pro-government Islamic volunteer militia, Basij, at the scene, shouting slogans against Mousavi, Norooz said.
It was not immediately possible to independently confirm the report, which came 10 days after security forces clashed with Mousavi supporters and arrested at least 10 of them during annual anti-Israel rallies in Tehran.
The September 18 clashes in Tehran were the latest sign of continuing discontent about the election, which the pro-reform opposition says was rigged to secure Ahmadinejad's re-election.
The authorities deny charges of vote rigging.
Iran's Revolutionary Guards largely quelled the huge opposition protests that erupted in the days after the vote, but pro-Mousavi supporters have continued to stage sporadic rallies.
Some pro-reform websites say Mousavi supporters will gather again on Tuesday to mark his birthday.
The election plunged Iran into its deepest internal crisis since the 1979 Islamic revolution and exposed deepening establishment rifts.
Thousands of people, including senior reformist figures, were detained after the election. Most have since been freed, though more than 100 remain in jail accused of orchestrating post-election street unrest.
The opposition say more than 70 people died during the unrest, more than double the official estimate.
(Editing by Diana Abdallah)