The three courts in the cities of Urumqi, Kashgar and Aksu also levelled charges of making explosive devices, promoting religious extremism and plotting "holy war", Communist Party mouthpiece the People's Daily said on its website (www.people.com.cn).

While it did not give the ethnicity of those sentenced, judging from their names they were all Uighurs, a Muslim Turkic-speaking people who call Xinjiang home, many of whom chafe at Beijing's rule and restrictions on their religion and culture.

"A vast amount of evidence shows that the accused criminals carried out a lot of preparatory work in planning violent terror activities and set up a formal terror organisation," the report said.

"They bought, produced and copied mobile transmitters, discs and publications which promoted separatism, religious extremism and violent terror and proactively spread them around," it added.

"Some members of the terror organisation made explosives and carried out test explosions."

China blamed violence in Xinjiang - strategically located on the borders of Afghanistan, Pakistan, India and Central Asia - on Islamic separatists who want to establish an independent state of "East Turkestan".

Some Chinese officials have blamed attacks on Muslim militants trained in Pakistan.

But many rights groups say China overstates the threat to justify its tight grip on the region.

Dilxat Raxit, spokesman for the exiled World Uyghur Congress, said the government had politicised the case and used terrorism as an excuse to punish Uighurs who don't agree with the system.

"The aim is to terrorise Uighurs into abandoning their rights," he said in an emailed statement.

Beijing has shown no sign of relaxing its control in Xinjiang, a vast swathe of territory accounting for one-sixth of China's land mass which holds rich oil, gas and coal deposits.

In July 2009, regional capital Urumqi was rocked by violence between majority Han Chinese and minority Uighurs that killed nearly 200 people.

Since the unrest, China has turned its attention to boosting development in Xinjiang and providing greater job opportunities, especially for Uighurs, to try to address some of the root causes of the violence. (Reporting by Ben Blanchard; Editing by Nick Macfie)