A pair of trucks smashed through metal barriers and plowed through crowds of early morning shoppers Thursday in the far western city of Urumqi, capital of the volatile Xinjiang region, killing 31 and wounding more than 90. It was the latest and bloodiest in a rising number of increasingly bold attacks by extremists among the Turkic Muslim Uighur ethnic group that is native to the area.
Here is some background on the region:
WHAT IS BEHIND THE VIOLENCE?
Tensions have been simmering in Xinjiang for years, but Uighur discontent seems to be growing over restrictive Chinese practices such as refusing to allow women to wear traditional head scarfs or young men to grow beards.
China has also been gradually phasing out the use of the Uighur language in education, throwing Uighur teachers out of work and adding to concerns that Uighur culture is under siege.
Uighurs feel marginalized as the benefits of growth and resources exploitation accrue to Han Chinese migrants who have flooded the region in recent decades. Add to that the influence of global militant Islam and the sense that Muslims elsewhere are standing up for their religion, and it creates a highly combustible mix.
ARE OUTSIDERS INVOLVED?
China says the violence is not attributable to religion or ethnicity, but is orchestrated by separatists and malcontents supported by instigators overseas.
Specifically, it blames a Uighur military group known either as the East Turkistan Islamic Movement or the Turkistan Islamic Party. While Uighurs are known to be among Islamic militants hiding across the border in Pakistan's lawless northwestern region, it isn't clear whether such a group exists and is capable of organizing and carrying out violence in Xinjiang.
Uighur militants occasionally turn up in propaganda videos to either praise or take credit for attacks within China. There is also a large network of activists in the Uighur diaspora who call for a peaceful struggle against the authorities. They are led by US-based Rebiya Kadeer, whom China imprisoned, then exiled and now accuses of having been behind 2009 ethnic riots in Xinjiang that left almost 200 people dead. She denies the allegation.
Read: 31 killed, 90 hurt as explosions rock China's Xinjiang
HOW HAS CHINA RESPONDED?
Beijing rules Xinjiang with an iron fist and has ignored Uighur demands and even calls from within the Chinese political system to reconsider some of its most restrictive policies.
This position was reinforced by President Xi Jinping's recent visit to region when he visited a paramilitary unit, observed a military exercise and vowed that the government would "make terrorists become like rats scurrying across a street, with everybody shouting 'Beat them!'"
The other aspect of Beijing's policy has been to pour resources into the area to promote rapid economic growth that it hopes will placate Uighur critics and tie the region ever closer to the rest of China.
WHAT IS THE REGION'S HISTORY?
The arid Central Asian region has for centuries occupied a position along the Chinese geographic and cultural periphery and was not under Chinese control for much of that time. The ancient "Silk Road" ran through the region, making it a key route for trade and the transmission of foreign concepts such as Buddhism.
It was ruled by a pair of independent Uighur republics in the first half of the last century, but was brought firmly under Chinese control after the communist seizure of power in 1949. Large numbers of Han Chinese began moving to Xinjiang, including those in military production units that act almost as mini-states unto themselves.
Officially, it is called the Xinjiang Uighur Autonomous Region, not a province, although the distinction is essentially meaningless. Uighur activists call the region East Turkistan.
WHO ARE THE UIGHURS?
The Uighurs are Central Asian people who are ethnically, culturally, linguistically and religiously distinct from Han Chinese.
They are distantly related to the people of modern Turkey, where thousands of Chinese Uighurs live in exile. There about 10 million Uighurs in China, mostly in Xinjiang, but also scattered throughout the country, where they work in factories and restaurants that are known for their distinctive cuisine based around lamb kebabs and flat bread known as nan. They are generally poorer and less educated than Han Chinese, a result, Uighur activists say, of linguistic bias and economic marginalization.