A top official from China's restive Xinjiang region said Thursday the evidence against a prominent Uighur academic whose detention has been condemned by Washington was "irrefutable".

Ilham Tohti, an economist who teaches at the Central University for Nationalities in Beijing, has been a vocal critic of Beijing's policies toward his mostly Muslim Uighur minority, who are concentrated in Xinjiang.

He has been charged with separatism, which can carry the death penalty.

"The facts are clear and the evidence is irrefutable," Xinjiang regional government chairman Nur Bekri said, according to the official Xinhua news agency.

Bekri was speaking to reporters on the sidelines of the rubber-stamp National People's Congress (NPC) at the Great Hall of the People, five days after a group of machete-wielding assailants killed 29 people and wounded 143 at Kunming railway station.

The attack has been dubbed "China's 9/11" by state media and officials have blamed separatists from Xinjiang.

Chinese authorities detained Tohti at his Beijing home in January, charging that he had "organised a group with the disguise of his identity, colluded with leaders of overseas East Turkestan separatist forces, and sent followers overseas to engage in separatist activities".

The move has drawn condemnation from campaign groups, the United States and European Union.

Tohti's wife told AFP in January that police did not follow any legal procedures while forcibly detaining him in front of his two young children.

But Bekri defended China's handling of the case on Thursday.

"China is a country ruled by law," he said, according to Xinhua. "We will safeguard his legal rights while he is under investigation."

During a meeting of the Xinjiang delegation at the NPC, members spoke for more than two hours before the topic of violence was raised -- and even then, officials appeared hesitant to address it.

Bekri said terrorism was "anti-society, anti-humanity and anti-civilisation" and "must be the common enemy of those of every ethnicity in Xinjiang as well as all of China".

"Violent terrorism cannot represent any ethnicity, and it cannot represent any religion," he said, adding that terrorists have struck in all parts of China and "do not distinguish between different ethnicities, man or woman, old or young".