Last week it was Green Dam. Before that it was Iran. Now it's Xinjiang, China's huge northwestern province, where the battle between censors and users goes on.
Some 156 people died and more than 800 were injured in riots in Urumqi, the provincial capital, on Sunday, according to the official Xinhua newsagency.
The city of 2.3 million has been locked down. Cellphone and internet access have been cut, and IDD calls into the province are barred.
Twitter, YouTube the Chinese micro-blogging service Fanfou were blocked from Monday afternoon. Internet searches for keywords such as "Urumqi" have been blocked.
To get around the censors, net users adopted the practice of "tomb-digging" where they will resurrect an old uncontroversial item and begin posting comments below.
In contrast with the tight internet censorship, Chinese authorities have aired news on the event in the mass media, blaming the violence on pro-independence forces, and have taken local journalists to Urumqi to see the aftermath at first hand.
The internet seems to have played a role in sparking the riot, which reportedly follows a brawl between Chinese and Uighur workers in factory in Shaoguan, thousands of kilometers away in Guangdong province.
Han Chinese killed at least two Uighurs in the violence, but photos appeared online showing a pile of corpses, leading people to believe that many more had died. The issue was hotly-discussed on local bulletin boards and on QQ, China's IM service, with Uiqhurs - the Muslim minority in Xinjiang - calling for protests.