Authorities launched a crackdown yesterday after over 2,000 teachers from across Iran gathered outside parliament carrying placards and chanting "Free those arrested," the Paris-based National Council of Resistance of Iran (NCRI) said.
Anti-riot police on motorbikes roamed the streets and there was a heavy security presence in metro stations, the group of Iranian pro-democracy activists in exile said in a statement.
"The number of those arrested in today's teachers' protest gathering in Tehran has reached 200," it said.
Protesters had gathered demanding the release of political activists such as Esmael Abdi, the head of the teachers' union, who are "imprisoned for their defence of teachers' rights," the group said.
The NCRI is a coalition of Iranian opposition groups, including the popular People's Mojahedin Organization of Iran which was struck off the US blacklist of designated terror groups in 2012 and a similar EU list in 2009.