Chinese authorities shut down blogs, Internet forums and social media sites such as Twitter in an apparent attempt to stem online political discussion ahead of Thursday’s 20th anniversary of the bloody crackdown on 1989’s Tiananmen Square pro-democracy protests.

As in past years, dissidents were rounded up and shipped out of Beijing and foreign media reports on the protests and continuing calls for an independent investigation into the events of June 3-4, 1989, have been blocked.

However, the cut off of Internet sites marks a new chapter in the authorities’ attempts to muzzle dissent, one that testifies to the burgeoning influence of such technology among young Chinese in an authoritarian society where information is tightly controlled.