On Monday, a knife-wielding gang attacked a police station and government offices triggering clashes that killed "dozens" of Uighur and Han Chinese civilians, according to state media outlet Xinhua.
But activists disputed this account and said that local Uighurs were protesting against a Chinese crackdown on the observance of Ramadan, which ended on Monday.
Reports surfaced earlier this month that some government departments in Xinjiang were banning Muslim staff from fasting during Ramadan, and several university students told the BBC that they were being forced to have meals with professors.
There has been an upsurge in Xinjiang-linked violence that authorities have attributed to Uighur separatists.
In May at least 31 people were killed when two cars crashed through an Urumqi market and explosives were thrown. In March, a mass stabbing at Kunming railway station killed 29 people.
In response Chinese authorities have launched a year-long security campaign which includes increased police and troop presence in key cities and towns in Xinjiang. Scores of people have been arrested, and some sentenced to lengthy jail terms or death.