Chinese police shot dead six people during a "terrorist" attack in the restive western region of Xinjiang and six more died when explosives they were carrying detonated, state media said, as officials accused a prominent academic of aiding militants.

Police came under attack on Friday by a group throwing explosive devices in Xinhe county, the official news agency Xinhua said on Saturday, citing regional authorities, the latest violence to jolt an area with a large Muslim population.

Five suspects were captured and one policeman was slightly wounded, Xinhua said.

Xinjiang has been the theatre of numerous incidents of unrest in recent years, which the government often blames on the separatist East Turkestan Islamic Movement (ETIM), although experts and rights groups cast doubt on its existence as a cohesive group.

Around 100 people, including several policemen, have been killed in violence in Xinjiang since last April, according to state media reports.

Many rights groups say China has overplayed the threat posed by militants from the large Uighur minority, Muslims who speak a Turkic language, to justify tough controls in energy-rich Xinjiang. The region lies on the borders of ex-Soviet Central Asia, India and Pakistan.

Eleven people believed to be members of a militant group of Uighurs were killed in Kyrgyzstan after illegally crossing into the former Soviet republic from China, Kyrgyz border guards said on Friday.

Police in Xinjiang's regional capital Urumqi said on Saturday a well-known, Beijing-based Uighur economics professor, Ilham Tohti, was being investigated for promoting Xinjiang's independence and abetting separatists.

Tohti was detained in Beijing last week, prompting concern from both the United States and European Union.

Tohti used his classes to laud the attackers in recent militant incidents as "heroes", "inciting the students to hate the country, hate the government and seek to overthrow it", Urumqi police said on their official microblog.

The Chinese-language statement implied a link with ETIM, but a later English translation by Xinhua did not use such specific terms.

"Ilham Tohti used his position as a teacher to entice, lure and coerce certain people to form a gang, colluded with leaders of overseas East Turkestan separatist forces, and sent followers overseas to engage in separatist activities," the statement said.

Tohti also sowed misinformation and rumors and "agitated for Xinjiang independence", the police said, adding they had "cast-iron evidence" against him.

Tohti's wife, Guzailai Nu'er, said on Sunday she thought the accusations were ridiculous.

"Do they really think the university would allow him to say such things in class? He's just an ordinary teacher. Why are they saying these things?" she told Reuters by telephone from her house, which is under close watch by police.

"And all this stuff about East Turkestan elements. What rubbish."

Nu'er said she still had no idea where he husband was being detained because authorities had not told her anything and were following her every move.

Tohti has championed the rights of the Uighur community in Xinjiang, and has challenged the government's version of several incidents involving Uighurs, including what Beijing says was its first major suicide attack involving people from Xinjiang in Beijing's Tiananmen Square last year.