A prominent scholar from China's mostly-Muslim Uighur minority will deny separatism at his trial Wednesday, as critics warn the prosecution -- in which he faces a life sentence -- will worsen tensions in violence-wracked Xinjiang.

Ilham Tohti, a former economics professor at a university in Beijing, is due in court in the Xinjiang capital Urumqi.

The Uighur homeland has seen escalating violence between locals and security forces in the past year, with hundreds dead, and Beijing has launched a crackdown on "separatists" and "terrorists".

But the United Nations, the European Union, the United States and several human rights groups have called for the release of Tohti, an outspoken critic of China's policies towards Uighurs in Xinjiang.

His prosecution -- almost certain to result in a guilty verdict -- risks silencing moderate Uighur voices and cutting off the possibility of dialogue, critics say.

Tohti was detained in January after he condemned the government's response to a suicide car attack in Beijing's Tiananmen Square which the government blamed on Xinjiang militants.

He has been denied food and kept in shackles during his detention, according to his attorney Li Fangping.

Prosecutors will argue that Tohti's writings on his website Uighur Online, and his lectures at the Minzu University in Beijing, show that he was a leading member of a "separatist criminal organisation", Li added.

In interviews, Tohti has stated his opposition to independence or separatism.

"Tohti has consistently, courageously, and unambiguously advocated peacefully for greater understanding and dialogue between various communities, and with the state," said Sophie Richardson, China director for US-based campaign group Human Rights Watch.

"If this is Beijing's definition of 'separatist' activities, it's hard to see tensions in Xinjiang and between the communities decreasing."

- 'They follow me everywhere' -

Separatism charges can carry the death penalty in China, but the wording of the indictment means life imprisonment is the heaviest sentence Tohti can face, lawyers say.

"Ilham will not accept the charge," said Liu Xiaoyuan, his second defence lawyer. "Looking at his articles and statements we haven't seen anything which would constitute separatism."

"A scholar expressing opinions on current events is not the same as separatism," he added.

Tohti's wife Guzaili Nuer, who will attend the trial along with three of Tohti's brothers, told AFP that she is continually tailed by security agents.

"They follow me everywhere, they are outside my brother's house as I speak," she said.

"I'm worried about (Tohti's) health, he has heart and stomach troubles, and he hasn't been allowed to visit a hospital," she added.

Nuer and three other family members will be allowed to attend the trial.

Around eight diplomats from countries including Germany, Britain and Canada have travelled to Urumqi for the hearing, although they are unlikely to be allowed to enter the courtroom.

Chinese courts are tightly controlled by the ruling Communist party and have a near-100 percent conviction rate in criminal cases.

Tohti devoted decades to researching government policy towards Uighurs, about 10 million of whom live in Xinjiang, a vast, resource-rich and strategically important region which abuts central Asia.

China blames ongoing unrest in the region on organised terrorists, while rights groups say cultural and religious repression of Uighurs has stoked violence.

As a professor and writer, Tohti was known for his moderate stance on Uighur issues but was repeatedly subject to house arrest and prevented from leaving the country.

In a 2011 essay, Tohti wrote: "I earnestly hope that my homeland can become as prosperous and developed as the rest of China. I worry about my homeland and my country falling into chaos and division."