Most opposition pro website and blogs are claiming that the rally was attended by 120,000 people.
More than 200 students of the Mashhad Open University in north-eastern Iran had been arrested, opposition websites reported.
A Malaysian opposition website is shut down by its British web-hosting company amid claims of "political censorship" from the opposition.
Witnesses and opposition websites reported the following incidents:
Rahesabz.net, an opposition website said that protesters have also gathered in front of state TV in north Tehran.
But he says in a statement posted Thursday on several opposition websites that he's decided to resign that post.
Other independent opposition websites were blocked at the same time.
Foreign-based opposition websites are blocked.
In 2008 Magomed Yevloyev, owner of the highly critical opposition website Ingushetia.ru, was killed while in police custody.
An opposition website, Ethiopian Review, reported that he had died of a heart attack.