The detention of Ali Nikunesbati, the spokesman for the Office for Strengthening Unity (Daftar-e Tahkim-e Vahdat), is the sixth of a student activist in the past 10 days in Tehran.
His brother Mohammad told RFE/RL's Radio Farda today that Intelligence Ministry agents detained Nikunesbati at his father's home and confiscated some of his personal belongings.
"They behaved badly [and] they shouted at us, 'Sit here, [and] sit there!,’ ” he said. “They were armed [and] they created a very bad atmosphere. They told [Ali Nikunesbati] to sit down and be silent. They searched our house for about an hour. They searched everywhere."
He added that officials did not inform the family why Nikunesbati was arrested or where he was being held.
Nikunesbati had been released on bail after his arrest in July in connection with his role in a protest to condemn the jailing of student activists.
His detention comes after another student leader, Ali Azizi, was detained on November 4.
Human rights advocates and student groups in Iran have expressed concern over what they describe as renewed government pressure on universities and student activists.
In recent weeks, students in Tehran have staged at least three protests against the crackdown on academic institutions.