The Syrian Observatory for Human Rights said several people were injured by tear gas and live ammunition.
Protests were reported elsewhere, a day after activists called for rallies in solidarity with students in Aleppo.
Observers say anti-government sentiment is rising there, after security forces killed students in a raid in early May.
Videos posted by activists show hundreds of people taking part in anti-government rallies in various parts of Aleppo.
Syria’s second city has so far not experienced the violence seen in other cities during the uprising and has remained largely loyal to the government of President Bashar al-Assad.
Analysts say its ability to keep control of Aleppo is one of its key tests.