Activist Dilxat Raxit, spokesman for the Germany-based World Uighur Congress, said witnesses heard "fierce gunfire" and saw at least 20 Uighurs arrested - part of what he says is a wider, ongoing crackdown. He did not give any other details.
A public security official said eight Uighurs - seven men and one woman - were involved. One man had been captured, but the others were at large, said the official, who refused to give his name as is common among Chinese officials.
Mu'erbiya, an official from Jiashi County's Communist Party propaganda office, said two police officers had died and an investigation was under way. Like some Uighurs, she uses one name.
Seven police officers were being treated at the No. 1 People's Hospital in Kashgar, about 60 miles west of Jiashi, including one for stab wounds, according to a woman at the hospital's emergency center who refused to give her name.
China has long said that militants among the region's dominant ethnic Uighurs are leading an Islamic separatist movement in Xinjiang, an oil- and gas-rich region on the border with Afghanistan, Pakistan and six Central Asian nations. The Uighurs are Turkic-speaking Muslims with a language and culture distinct from the majority of Chinese.
But critics accuse Beijing of using claims of terrorism as an excuse to crack down on peaceful pro-independence sentiment and expressions of Uighur identity.
Chinese Foreign Ministry spokesman Qin Gang on Thursday confirmed reports of the Jiashi incident but did not provide any details. He insisted that there were only sporadic tensions in Xinjiang.
"People of various ethnic groups coexist in harmony and equality, and the situation in Xinjiang is generally good," Qin said at a regular briefing. "This has nothing to do with any alleged persecution or oppression of the Uighur people."
He said that there was a handful of Uighur "terrorist forces attempting to create violence and split China" but that the government and authorities were cracking down on them.
The predominantly Muslim region saw three deadly attacks during and just before the Beijing Olympics. Videos also appeared online threatening the games.
The wave of violence began on Aug. 4, four days before the start of the competition, in the ancient Silk Road city of Kashgar near the border with Afghanistan and Pakistan. Two men stole a truck and rammed it into a group of police on their morning jog. The men continued attacking with homemade bombs and knives, killing 16 police.
Six days later, bombers struck in the west-central Xinjiang county of Kuqa, targeting a police station, government building, bank and shops owned by Chinese. Police said they killed 10 of the attackers - including one woman - while a security guard and a bystander died in the violence. State media said another attacker, a 15-year-old girl, was injured.
On Aug. 12, attackers jumped from a vehicle and stabbed civilian guards, killing three of them at a roadside checkpoint in Yamanya town, near Kashgar. The assailants escaped.
No one has claimed responsibility for any of the incidents, though government officials have suggested terrorism is behind the violence.
Citing local Uighurs, Raxit, the activist, said large-scale arrests have been taking place in Kuqa and Kashgar since the attacks and residents of Kuqa are prohibited from traveling outside of the area. Checkpoints also have been set up, he said, adding that Wednesday's incident has triggered even tighter restrictions.
"It is part of China's worsening crackdown in the area," Raxit said in a statement. "The international community should prevent the Chinese government from carrying out their systematic crackdown policies on the Uighurs."
Police in Kuqa refused to comment on the current situation and telephones at police headquarters rang unanswered in Kashgar.
The Uighurs suffered greatly in the 1960s and 1970s when the government - caught up in Marxist revolutionary fervor - viewed religion as well as minority languages and culture as divisive remnants of feudalism that should be abolished.
In the 1980s, the government adopted a more liberal political and cultural policy in Xinjiang, but in the following decade resorted to a hardline policy after scattered incidents of unrest.
