"Police say it was an intentional act because the suspect was carrying explosive devices,'' Hou Hanmin, a spokeswoman for the Xinjiang government, said.
Authorities said that the assailant was injured in the explosion and captured immediately, though they did not say whether the suspect was a man or a woman.
Melissa Chan, Al Jazeera's correspondent in the regional capital, Urumqi, said: "It could well have been that this small vehicle was carrying some flammable liquid and that it could have been an accident.
"But what the officials made very clear is that was intentional and that this was not an accident.
"The other thing that we are getting is that all of the dead and injured are ethnic minorities. In other words, no one of Han Chinese ethnicity was hurt or killed in the incident.
"So it is unclear at the moment what the intentions were."
Xinjiang has suffered ethnic conflict and separatist violence in the past. Last July, minority Turkic Muslim Uighers and China's majority Han clashed in ethnic riots, leaving nearly 200 people dead.
Hundreds of people were arrested following the riots and about two dozen were sentenced to death.
Human rights groups have complained that many other Uighurs remain unaccounted for, believed to be in custody.
Dilxat Raxit, a spokesman for the overseas World Uyghur Congress, accused the Chinese government of "systematic oppression" of his community since unrest last summer.
More than eight million Uighurs live in Xinjiang, a vast, arid and resource-rich region which borders Central Asia.
Many Uighurs are unhappy with what they consider repressive rule from Beijing and unwanted immigration into the region by ethnic Han Chinese.
Living standards have improved in the region in recent years, mainly due to China's economic growth, but Uighurs complain that most of the gains go to the Han.
In June of this year, police arrested ten people who were allegedly behind a series of attacks in the region.
Police said arrestees included members of the East Turkestan Islamic Movement (ETM), a mainly Uighur group seeking independence for Xinjiang, which the US and UN have listed as a "terrorist" organisation.