China has sentenced 20 men to terms of up to life imprisonment for involvement in terrorism and "inciting secession" in the country's ethnically-divided western region of Xinjiang, state media said.

The men were convicted of a series of crimes, including circulating religious extremist material and attempting to set up an Internet chat room to promote "ethnic separatism", the Tianshan news website said.

The local government mouthpiece also said the men were accused of spreading information about the East Turkestan Islamic Movement, which is considered a terrorist organisation by Beijing, the United States and the United Nations.

One of the men was accused of attacking "innocent people" and smashing cars, motorbikes and other property, it added Tuesday, after the men were sentenced.

An official in the Xinjiang region publicity office told AFP Wednesday they had no details on the case, while the local court and police were unavailable for comment.

Xinjiang is home to around nine million Uighurs, many of whom complain of religious and cultural repression by Chinese authorities -- accusations the government denies.

The sentences were Wednesday branded as "repressive" by an overseas Uighur group.

"It is a specific repressive tool of the Chinese authorities to suspect an Uighur of terrorism and to hand them a heavy sentence," said Dilxat Raxit, a spokesman for the exiled World Uyghur Congress in an email to AFP.

Sources told the organisation the men were detained after they listened to Uighur-language programmes on US-based Radio Free Asia and downloaded videos from the YouTube website.

"They also used the Internet to discuss religion and the importance of protecting ethnic culture and traditions," Raxit added.

Xinjiang has been under strict security since July 2009, when bloody ethnic riots broke out in the capital Urumqi.

The government says nearly 200 people were killed and 1,700 injured in the violence, which shattered the ruling Communist Party's claims of harmony and unity among China's dozens of ethnic groups.