The Associated Press
The official IRNA news agency and state Press TV say there were 16 defendents in court for the trial's opening on Saturday.
At least eight people were killed and hundreds more were arrested during the December clashes between opposition activists and security forces. The violence was the worst since authorities launched a harsh crackdown immediately after Iran's disputed presidential election in June.
Since August, Iran's hardline government has tried more than 100 political activists. Eleven people have been sentenced to death. More than 80 others have received prison terms.