With independent media coverage of Iranian protests restricted by authorities, witnesses are reaching out online and by telephone to report what they see on the streets of Tehran.
Opposition Web sites said protesters had planned to gather Saturday in Revolution (Enghelab) and Freedom (Azadi) Squares, two of Tehran’s main areas.
But witnesses told VOA Persian News Network and other news agencies they saw large numbers of police gathered in the streets, blocking the demonstrators.
Near Freedom Square, the witnesses say police clashed with thousands of protesters, arresting some and using tear gas, batons and water cannons on others.
Some witnesses also said they heard gunshots, but it is unclear who fired the shots. At least three helicopters were hovering over the area.
At other places in the capital, witnesses say protesters attacked authorities, setting some of their motorcycles on fire.
News agencies are relying heavily on information published by Iranian citizens through social media services, such as Twitter, Facebook and YouTube.
On Friday, Facebook announced it is making its Web site available in Farsi, so Iranians can use the service in their native language.
Google also introduced a new Farsi translating tool.