After the news came out, the fans showed a banner saying, "You never knew how to replace someone."
Officials said they did not know what the banner said.
A banner hung in one building by student militants says the congress should be "a process, not an event."
"We're fed up," banners held by thousands of people said.
Some of them carried banners saying "Better dead than coed."
Video from the city showed protesters waving banners saying, in English, "we want freedom".
The company's main website was down on Sunday, with a banner saying the "site is currently undergoing maintenance".
The banner said, 'No man can serve two masters.
"We are striking against our bosses' arrogance," one banner said.