A nationwide rally on Monday to mark the killing of three students under the Shah turned violent when students clashed with security forces armed with batons and tear gas in the largest anti-government protests in months.

"From now on, we will show no mercy toward anyone who acts against national security. They will be confronted firmly," said prosecutor Gholamhossein Mohseni-Ejei, according to the official IRNA news agency.

Witnesses said scuffles occurred between students loyal to opposition leader Mirhossein Mousavi and others who support hardline President Ahmadinejad in Tehran universities on Tuesday.

Reuters could not confirm the report independently because journalists working for foreign media have been banned from leaving their offices from December 7 to December 9.

Mousavi's website, Kaleme, said security forces had a heavy presence around Tehran universities. It said Mousavi was harassed outside his office on Tuesday.www.reuters.com/article/idUSTRE5B72WL20091208

Read More