Video circulating on social media appears to show Iranian riot police firing tear gas on crowds in Tehran’s Azadi Square over the weekend. The images also appear to show several people being detained. CNN cannot independently verify these videos.

Security forces were deployed in key areas of the capital, including Azadi Square near Sharif University, Enghelab (Revolution) Square near Tehran University, and Ferdowsi Square.

Fully equipped riot police were on patrol, accompanied by water cannons and black vehicles that are sometimes used as mobile detention centers.

In one video posted on social media, protesters chanted for Supreme Leader Ayatollah Ali Khamenei to step down and for those responsible for downing the plane to be prosecuted. “Death to the dictator,” some chanted. In one video, demonstrators chanted, “Khamenei have shame. Leave the country.”

Another shows what looks like people running away from what appears to be some sort of smoke or gas.

A third video shows people coughing as the smoke gets nearer. Someone is heard shouting ““if the cars go, they will send in the bikes,” likely a reference to the fact that Iran’s security forces often come in on motorbikes wielding batons to break up protests.