Outraged Western powers have rounded on China over a life sentence handed to a prominent Uighur academic, accusing Beijing of silencing a moderate voice in a move that analysts say risks inflaming tensions in the restive Xinjiang region.

A court in China's far western Xinjiang region on Tuesday sentenced Ilham Tohti -- a persistent but moderate government critic who advocated for the rights of the mostly-Muslim Uighur minority -- to life in prison on charges of "separatism".

The decision was seen as unusually harsh -- it also includes depriving Tohti of political rights for life and the confiscation of his personal property -- and comes amid a broader crackdown on what the state claims is a terror-backed independence movement in Xinjiang.

The sentencing of the 44-year-old father of three drew strong condemnation from the United States and European Union, with both calling for his release.

The White House urged Chinese authorities to differentiate between "peaceful dissent and violent extremism".

"We believe that civil society leaders like Ilham Tohti play a vital role in reducing the sources of inter-ethnic tension in China, and should not be persecuted for peacefully expressing their views," the White House press secretary said in a statement.

The EU called the sentence "completely unjustified" and urged his immediate and unconditional release.

Foreign analysts were puzzled by the verdict, saying none of Tohti's writings or comments advocated a Uighur breakaway from China. They warned of a further rise in tensions in Xinjiang, which has been hit by a string of attacks on civilians and clashes which have killed at least 200 people in the last year.

"I think most observers of Xinjiang and Uighur issues will be very disheartened by this as it seems likely to add fuel to the fire of conflict in Xinjiang," Michael Clarke, an authority on Xinjiang at the Griffith Asia Institute in Australia, told AFP.

- US 'deeply disturbed' -

Resource-rich Xinjiang is home to about 10 million Uighurs, who have close linguistic and cultural ties to nearby Central Asian nations. In recent decades the region has also seen an influx of migrants from China's dominant Han ethnicity, which experts say has fulled Uighur resentment.

China blames the violence on "terrorist" groups seeking independence for the region, while rights groups say that cultural and religious oppression of Uighurs has fuelled resentment.

The attacks have grown in scale and sophistication and have spread outside the region, including a deadly rampage by knife-wielding assailants at a train station at Kunming in China's southwest in March, which left more than two dozen dead.

Police detained Tohti, who taught economics at a university in Beijing, in January after he criticised the government's response to a suicide car attack last October in Beijing's Tiananmen Square, which the government blamed on Xinjiang separatists.

Prosecutors at Tohti's trial in the Xinjiang capital of Urumqi presented videos of his university lectures and posts from his website Uighur Online as evidence that he had led a separatist group, said Li Fangping, one of his lawyers.

They also cited testimony from some of Tohti's students, around eight of whom have also been detained.

Secretary of State John Kerry said the United States was "deeply disturbed" by the life sentence, describing Tohti as "an important moderate Uighur voice".

"This harsh sentence appears to be retribution for Professor Tohti's peaceful efforts to promote human rights for China's ethnic Uighur citizens," he added.

Barry Sautman, an expert on ethnic politics in China at Hong Kong University of Science & Technology, said other Uighur intellectuals would be "really disappointed" by the sentence.

"They will have to wonder why he got such a harsh sentence compared to even the most prominent of Han intellectuals who is now sitting in prison for opposing the Chinese government, and that is Liu Xiaobo, who got 11 years," he said.

Liu was sentenced in 2009 after spearheading a bold petition for democratic reforms. He won the Nobel Peace Prize in 2010, sparking a vehement reaction from Beijing.

"Some people will of course draw the conclusion that if you are an ethnic minority person, particularly a Uighur, you are bound to get a harsher sentence than if you are not," Sautman added.