'Supporters of opposition leader (Mir-Hossein) Mousavi clashed with police in Haft-e-Tir Square and police fired two rounds of teargas to disperse the protesters,' the Jaras website said.
Because of a ban on foreign media reporting on illegal demonstrations, the report could not be independently verified.
Iranian hardline authorities have ordered their opponents to cease anti-government protests.
The authorities have signalled they will tolerate no more protests after eight people were killed in fiery rallies on Sunday during the Shia ritual of Ashura.
