Internet and some phone service was cut off in Urumqi, the capital of Xinjiang province, after members of the Uighur minority group clashed with Han Chinese in the city on Sunday.
The rioting, officially the most deadly violence in China in decades, gave release to simmering tension between the culturally distinct ethnic groups and to Uighur discontent with Chinese rule.
Over 1,000 people were injured, and China has arrested more than 1,400 people suspected of involvement, according to the official Xinhua news agency, which gave the current death toll.
The clashes follow an uprising in Tibet last year, after which China similarly blocked websites to prevent the spread of unofficial videos and accounts of the news. Demands for greater autonomy in Xinjiang and Tibet are hyper-sensitive issues that China views as a threat.
Shocked Chinese have turned to the Internet to discuss the event. But views expressed in online forums have largely hewed to the government's position on the riots, suggesting initial success for its efforts to control public opinion through the Internet and other media.
China is working to ensure that its take on the event dominates discussion in the media and online, and it is doing so more effectively than it did after the riots in Tibet, said Phelim Kine, a Hong Kong-based researcher for New York-based Human Rights Watch.
"There seems to have been a very steep and dramatic learning curve," Kine said.
China shut down the Internet in Urumqi the day of the riots, much faster than the 10 days it took to block YouTube after the Tibet uprising last year, when dozens of videos were uploaded.
Some unofficial videos of the rioting this week appeared on YouTube too, mainly showing hundreds of people marching peacefully through streets. But since Internet access was blocked in Urumqi, videos uploaded to the site have mostly drawn on clips from Chinese state media reports. Those reports have shown burning cars and bloodied Han Chinese in hospitals or lying on streets.
The switch in the dominant images reflects China's efforts to guide coverage of the event, said Kine.
China has encouraged migration to Xinjiang by Han Chinese, who are by far the country's majority. Uighur advocates say Han Chinese often get the better jobs in the province.
Online forums in China appear to have stepped up the message screening they usually practice to prevent sensitive material from appearing on their sites. Searches for "Urumqi" or "Xinjiang" in a Baidu forum on Tuesday returned no results, and a message that the material was temporarily barred from discussion "in accordance with relevant laws and policies."
Many messages that appeared in other forums criticised Uighur violence against Han Chinese. Some users posted pictures and video clips from the state-run media reports.
"People from Xinjiang can kill others without getting the death sentence?" one user said in the Tianya forum.
"I suggest sentencing all of them to death," another user replied.
"I strongly condemn this and resolutely support the government's decisions!" another user wrote in a forum on the Sina.com web portal.
Twitter remained blocked in China on Tuesday after it became inaccessible following the riots. YouTube has been blocked in China for months.
China has blamed a Uighur organisation it labels separatist for inciting the riots. The rioting was spurred by a deadly brawl over a week earlier between members of the two ethnic groups in a far-away southern Chinese city, Xinhua said. That fight left two Uighurs dead and dozens injured, the agency said.
A Chinese official confirmed the Internet had been switched off in parts of Urumqi to prevent the spread of the rioting, but did not say when service would resume, Xinhua said Tuesday.
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