TEHRAN A group of Iranian students gathered at Tehran University on Sunday to protest against the detentions of three fellow students last week, an Iranian news agency reported on Sunday.
ISNA, the students' news agency, said the three were held during a small demonstration at another university in the Iranian capital last Tuesday, which was held to protest against the suspension of some students.
"Imprisoned students must be freed," the students chanted, ISNA reported without saying how many they were. It was not clear why the students were arrested but another Iranian news agency had said last week's rally was illegal.
Student protests have been relatively rare in recent years in the Islamic Republic, which is locked in an escalating nuclear row with the United States and is often criticized by Western rights groups for acting against dissent at home.
But earlier in October, more than 100 students scuffled with police and hardline supporters of President Mahmoud Ahmadinejad on the campus of Tehran University outside a hall where the president was about to speak.
Liberal-minded students and academics have criticized Ahmadinejad for clamping down on dissent on Iranian campuses, although the president and his government insist they support free speech and welcome constructive opposition.
Students and activists say some of those who have spoken out against Ahmadinejad and his government in the past two years have been detained or blacklisted from university courses.
Protester Farbod Hashemi, quoted by ISNA, told the crowd at Sunday's rally:
"We have gathered here to again express our protest to everyone ... We use this open tribunal to say we are ready to sacrifice our lives for happiness and freedom."
Ahmadinejad swept to office in 2005 vowing to distribute Iran's oil wealth fairly and a return to revolutionary ideals.
Critics say his policies have stoked inflation and his fiery rhetoric has provoked Western nations to impose sanctions.