Internet users have not been able to go online in Urumqi, the northwestern Chinese city hit by ethnic violence that killed at least 140 people, residents said on Monday, Reuters reported.
Locals took to the streets on Sunday, some burning and smashing vehicles and confronting ranks of anti-riot police. Over 800 people were injured and police have arrested "several hundred" participants, the official Xinhua news agency said.
"Since yesterday evening I haven't been able to get online," store owner Han Zhenyu told Reuters by telephone.
"No Internet here, friends said they cannot log on, either," said a mobile phone seller who gave only his surname, Zhang.
News of the apparent outage was also spread by messages on social networking services like Twitter and its Chinese competitors.
"The incident has largely subsided, but armoured cars were still in town this morning. Internet in Urumqi is still down, someone said it would last for 48 hours," one user, who said he was in Urumqi, wrote on domestic site fanfou.com.
China has previously shut down communications in parts of Tibet where ethnic unrest had erupted or was feared.