On Tuesday, mobs of ethnic majority Han Chinese with meat cleavers and clubs reportedly roamed the streets looking for Muslim Uighurs who had launched earlier attacks in the country's worst ethnic violence in decades.
Rioting in the Xinjiang region broke out Sunday and killed at least 156 people, according to media reports. The new violence Tuesday came despite swarms of paramilitary and riot police enforcing a dragnet that state media said led to the arrest of more than 1,400 people in the often tense region.
Uighurs attacked people near Urumqi's railway station, and women in headscarves protested the arrests of their husbands and sons in another part of the city. For much of the afternoon, a mob of 1,000 mostly young Han Chinese holding cleavers and clubs and chanting "Defend the country" tore through streets trying to get to a Uighur neighborhood until they were repulsed by police firing tear gas.
The government slowed mobile phone and Internet services, blocked Twitter and censored Chinese social networking and news sites and accused Uighurs living in exile of inciting Sunday's riot. State media coverage, however, carried graphic video and pictures of the unrest -- showing mainly Han Chinese victims and stoking the anger.
Rioters on Sunday had overturned barricades, burned vehicles and clashed violently with police. State television aired footage of protesters kicking people and others sitting on the ground with blood on their faces.
Tensions between China's Han majority and the Muslim Uighur people periodically erupt into violence in Xinjiang, where the government tries to control religious and cultural life in order to maintain stability and encourage economic growth.
The violence is a further embarrassment for a Chinese leadership preparing for the 60th anniversary of communist rule in October and calling for the creation of a "harmonious society" to celebrate.
Years of rapid development have failed to smooth over the ethnic fault lines in Xinjiang.
Xinhua released a one-sentence report early Tuesday saying 156 people had died, but gave no information about how they died or how many were Han or Uighurs.
"This was a crime of violence that was premeditated and organized," said an unnamed official, quoted Xinhua.
He blamed the violence on the World Uyghur Congress led by Rebiya Kadeer, a Uighur businesswoman now in exile in the United States after years of prison and being accused of separatist activities, Reuters reported.
Witnesses and state media said the violence only started after police arrived to disperse a peaceful protest demanding action for two Uighurs killed last month during a fight with Han coworkers at a factory in southern China, according to the Associated Press.
Uighurs make up the largest ethnic group in Xinjiang, but no longer in Urumqi, where many Han Chinese migrants have settled.
Mary Kay Magistad, China correspondent for PRI's The World, explained the history of the tensions and the event that sparked the unrest in an interview on Monday:
U.N. Secretary-General Ban Ki-moon urged China and other countries with violent protests to use extreme care. He urged governments to "protect the life and safety of civilians," quoted the AP.
The Uighur community, both in China and abroad, drew attention recently amid a debate over the fate of 17 Uighur detainees held at the U.S. military camp at Guantanamo Bay who were cleared for release more than four years ago. The detainees were ultimately sent to a number of locations, including Palau and Bermuda.
The men claimed they could be tortured by Chinese authorities if they returned to their native Xinjiang province.
A statement from White House spokesman Robert Gibbs expressed deep concern over the reported deaths and called on "all in Xinjiang to exercise restraint."