At least 31 people were killed and more than 90 injured in an attack on a market in the city of Urumqi, capital of China's volatile Xinjiang region, in the deadliest incident since 2009.

Drivers reportedly rammed two vehicles into the crowded space, hitting pedestrians at random while detonating explosives. 

The New York Times offers some detail on what happened:  

One of the vehicles exploded in the market, Xinhua said, citing someone in the market who said that there had been a dozen big bangs. Saloshka, a woman who said she was about 100 paces from scene, said on her Sina Weibo account that the casualties were “elderly grandpas and grannies” at market early.

One man, who owns a supermarket near the scene of the attack, told the Associated Press that "I heard four or five explosions. I was very scared. I saw three or four people lying on the ground." The AP adds

Photos from the scene posted to popular Chinese social media site Weibo showed at least three people lying in a street with a large fire in the distance giving off huge plumes of smoke. Others were sitting in the roadway in shock, with vegetables, boxes and stools strewn around them.

The local  government issued a statement on the attack, calling it a "a serious violent terrorist incident of a particularly vile nature." Chinese President Xi Jinping said that he will "severely punish terrorists and spare no efforts in maintaining stability." 

It's not yet clear who perpetrated the attack, but most suspect that extremist Uighurs are responsible. Xinjiang has seen a recent spike in terror attacks by militant Uighur Muslims, who want independence in the region, claiming that Chinese rule is prejudiced against them as a religious and ethnic group. The Uighur minority maintains an uneasy relationship with the region's Han Chinese majority, and clashes between the two groups left 200 dead over several days of unrest in 2009. 

China has recently pledged to step up its anti-terror efforts. Earlier this week, the Chinese government put 39 people allegedly involved in terrorist activity in jail, and officials have arrested seven people suspected of contributing to last month's attack on a train station in Xinjiang, which left three dead (including assailants) and 79 injured.