An exile Uighur group on Tuesday demanded Chinese authorities allow independent investigations into a clash in Xinjiang where eight "attackers" were shot dead by police, the latest deadly incident in the largely Muslim region.

The Xinjiang regional government should "fully disclose all information" on the Monday violence and allow "an independent investigation to be conducted by international organs", the Munich-based World Uyghur Congress (WUC) said in a statement.

It also called on Beijing to open Shache county, where the conflict took place, to foreign media and government representatives "to allow transparency surrounding the narrative of the incident".

The area, around 200 kilometres (124 miles) south-east of Kashgar, is known as Yarkand in the Uighur language.

Chinese authorities have described the incident as an "organised and premeditated terrorist attack" on a local police station by a total of nine "terrorists" armed with knives and explosive devices, according to the state-run Xinhua news agency.

One of the "attackers" was held in the clash, it said, adding police confiscated 25 explosives and nine knives at the site of the "attack".

The group, led by two apparent Uighurs identified as Usman Barat and Abdugheni Abdukhadir, had gathered to watch terrorist videos and promoted religious extremist ideas since August, Xinhua quoted Xinjiang police as saying. They had also raised funds and made and tested explosives for planned terrorist attacks, it added.

Uighurs, who have followed Islam for centuries, are the largest ethnic group in Xinjiang, a sprawling and resource-rich region four times the size of Japan and rich in oil and natural gas.

The WUC alleged that the incident was another case of the government silencing dissent by killing Uighurs under the pretext of fighting terrorism.

"This incident testifies to a recent trend of state-sponsored violence used to quell Uighur dissent, whereby authorities ignore due process of the law, shoot and kill Uighurs, label them terrorists, and then use counter-terrorism to justify the unlawful killings," said WUC president Rebiya Kadeer in the statement.

Authorities have blamed "terrorists" for a series of similar incidents this year in Xinjiang.

Rights groups and outside scholars, however, say unrest is spawned by cultural oppression, intrusive security measures and a wave of immigration by China's Han majority.

Information in the area is tightly controlled and difficult to independently verify.

In the worst outbreak of sectarian violence in recent years in China, around 200 people died and more than 1,600 were injured while hundreds were arrested in riots in the Xinjiang regional capital Urumqi in July 2009.