Eyewitnesses say that police used tear gas and batons against the protesters. A number of people were arrested, according to reports by Iran's official news agencies.
The protest marks the first instance of unrest over the plunging value of Iran's currency, the rial, which has reached a record low, losing about one-third of its value since last week.
Several amateur videos, said to be from the protest in Tehran, show hundreds of people walking in the city center. RFE/RL is not able to fully confirm the authenticity of the videos.
In this video recorded with a cell phone, protesters are apparently expressing anger over Iran's support for the Syrian regime.
"Leave Syria alone, think about us," they chant.
In this video, protesters call on Tehran's bazaar merchants to support them: "Dear prideful bazaaris, support, support."
They also demand the closure of the shops and businesses: "Close down, close down."
Well known Iranian activist Vahid Online posted this video, in which protesters are marching on Ferdowsi Street and chanting some of the slogans of the 2009 antigovernment protests, including "Don't be afraid, we're all together" and also "No to Syria, No to Lebanon, may my life be sacrificed for Iran."
The opposition Kalame website reports that "Death to Syria," "Death to the dictator," "Allah Akbar," and "The dollar should be halved" were among other slogans that were chanted in the Iranian capital on October 3.
Some chants also reportedly targeted President Mahmud Ahmadinejad, who has been accused of massive economic mismanagement and inefficiency in dealing with the current crisis. Ahmadinejad said on October 2 that the devaluation of the rial was in part caused by the sanctions Iran is facing over its sensitive nuclear work.
The plunge of the rial is causing anxiety and pain among many Iranians.
A merchant in Tehran told RFE/RL that many people are scared about the future.
"Everyone is very concerned and frightened. I can say that everyone is very confused. Of course, this general atmosphere has cast a shadow over Iran for a long time," he said.
"Nobody knows what's going to happen to them next week. The situation is getting very bad. You never see a smile on anybody's face anymore."
-- Golnaz Esfandiari