Police in China's restive western region shot dead 13 assailants who rammed a truck into a police building and set off explosives in an attack that also wounded three officers, state media said.
The Tianshan website said in a one-line report that no civilians were hurt in the attack in Kashgar prefecture in Xinjiang's south west.
Dilxat Raxit, spokesman for the German-based group World Uyghur Congress, said he called several residents in the Yecheng area who described hearing rapid gunfire, likely from police, before an explosion rang out. He said that authorities quickly placed the county under martial law and started rounding up people in a nearby market.
"It's undeniable that the armed police are using excessive force to deal with the unrest in the region. Why did they need to shoot them dead on the spot?" Mr Raxit said. "If they just injured them they would still have a chance to be put through the legal process."
It was the latest in a series of attacks pointing to growing unrest in the sprawling region of Xinjiang, where the native Muslim Uighur people want more autonomy from Beijing. Last month, a market bombing killed 43 people in Xinjiang's capital, Urumqi.
Chinese authorities have blamed the attacks on extremists bent on overthrowing Beijing's rule. The government says the assailants have ties to Islamic terrorist groups abroad, but provides little direct evidence.
The government has sought to stem the attacks by handing down heavy punishments to people authorities say organised, led and participated in terrorist groups, committed arson, murder, burglary or illegally manufactured explosives. Earlier this month, China executed 13 people in Xinjiang for such crimes.
Uighur activists say public resentment against Beijing is fuelled by an influx of settlers from the Han majority in the region, economic disenfranchisement and onerous restrictions on Uighur religious and cultural practices. China says it has made vast investments to boost the region's economy and improve living standards.