WASHINGTON, May 22  -- The United States condemns the " horrific" terrorist attack in Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region, the White House said Thursday.

"This is a despicable and outrageous act of violence against innocent civilians, and the United States resolutely opposes all forms of terrorism," White House spokesman Jay Carney said in a statement.

Carney said the United States is "aware of reports that the attack resulted in the death of 31 citizens and the injury of 90 more."

"We offers our condolences and sympathies to the victims, their families, and all those affected by this attack," he added.

Two vehicles, without license plates, broke through roadside fences and plowed into people at an open-air market in Urumqi on Thursday morning. Explosive devices were set off, causing the deaths of at least 31 people and injuring 94 others.

In response to the attack, Chinese President Xi Jinping pledged to severely punish terrorists and spare no efforts in maintaining stability, asking local authorities to solve the case quickly, put the injured under proper care and offer condolences to families of the victims.