Religious extremists were responsible for a "terrorist assault" in the far western region of Xinjiang that left 11 people dead, state media said, adding details about the latest violence to hit the restive area, which has a large Muslim population.
An investigation showed Friday's attack in Wushi county, close to the border with Kyrgyzstan, was an "organised, premeditated terrorist assault targeting the police", Xinhua reported, citing Xinjiang police.
A group of 13 terrorists trained for six months under a man named Mehmut Tohti, who had "spread religious extremism" for three years, Xinhua said.
It did not identify him as one of the mainly Muslim Uygur people who call the region home, but his name suggests he is one.
Xinhua said that the extremists listened to audio recordings and watched videos of terrorist acts before the attack on police vehicles.
Since January the group had been producing explosive devices and knives, the report said.
The agency earlier reported that the group put gas cylinders in their car in a bid to use it as a bomb.
Eight were killed by the police and three died "by their own suicide bomb", Xinhua said.
Many vehicles in the region use liquefied natural gas as fuel.
Two civilians and two police officers were injured in the incident and five police vehicles were damaged or destroyed, Xinhua said.
Xinjiang has been convulsed for years by violence that Beijing blames on Islamist militants and separatists who it says want to establish an independent state called East Turkestan.
But exiles and many rights groups trace the cause to Beijing's policies, including curbs on Islam and the Uygur culture and language, charges the government denies.
More than 100 people, among them several policemen, have been killed in violence in Xinjiang since April, state media have reported.
Kyrgyzstan said last month its border guards had killed 11 people believed to be members of a militant group of Uygurs.
Rights advocates argue that mainland reports about violence there cannot be trusted and that the authorities restrict travel by journalists and do not allow independent and transparent investigations.