A court in China's far west has sentenced to death two teenagers for the killing of the head of the country's biggest mosque, state media reported, in a case that highlighted divisions in the violence-wracked Xinjiang region.

The Kashgar Intermediate People's Court on Sunday handed down the death penalty to Gheni Hasan and Nurmemet Abidilimit "on charges of forming and leading terrorist groups and murder", the official Xinhua news agency said.

A third person, Atawulla Tursun, received a life sentence for "taking part in terrorist groups and murder", Xinhua said.

"The court said the gang, led by Gheni Hasan, was influenced by religious extremism and trained its members to murder patriotic religious figures," the report said.

The state-run China Daily newspaper on Monday gave Abidilimit's age as 19 and Hasan's as 18, though it identified Hasan as Aini Aishan, a Chinese transliteration.

Jume Tahir, the government-appointed imam of the 600-year-old Id Kah mosque in Kashgar, was killed on July 30.

The reports said Abidilimit and two others killed the imam, adding that the others were shot dead by police in an ensuing manhunt.

Citing the Xinjiang Daily newspaper, the China Daily said Hasan planned the killing because he believed the imam had distorted the meaning of the Koran, and that the killing of such an influential person would make an impact.

Xinjiang, home to China's mostly Muslim Uighur ethnic minority, has seen escalating violence which in the past year has spilled over into other parts of China.

Authorities have launched a crackdown and courts have meted out harsh sentences such as the death penalties given to three people earlier in September over a mass stabbing that left 31 people dead in the southwestern city of Kunming in March.

In August China announced the executions of eight people for "terrorist attacks", including three it described as "masterminding" a suicide car attack in Beijing's Tiananmen Square in October last year.

China blames unrest in the region on organised terrorists influenced by religious extremists and groups abroad.

Rights groups and analysts, however, say cultural and religious repression of Uighurs as well as massive immigration to the region by China's dominant Han ethnic majority have stoked tensions.

"The harsh sentences can't stop Uighur dissatisfaction," Dilxat Raxit, spokesman for exile group World Uyghur Congress, said in a message to AFP.

The Chinese government "should look for the root of this problem in its own policies", he added.

"Uighurs' religion and traditional lifestyle should be respected and provocations should be stopped to avoid new turmoil."