* Access to lawyer denied on "state secrets" grounds
* Case has caused U.S. and European outcry
* Rights advocate says China's handling of case is "highly irregular"
By Michael Martina
BEIJING, Feb 27 (Reuters) - A prominent Uighur economist who has been charged with separatism in China's far western Xinjiang region was denied access to legal counsel on Thursday, his lawyer said, on grounds that the case involves "state secrets".
The lawyer for Ilham Tohti, a professor who has championed the rights of Xinjiang's large Muslim Uighur minority, said he was given a notice that he could not meet his client, in detention in the region's capital, Urumqi.
Tohti's case is the latest sign of the government's hardening stance on dissent in Xinjiang, gripped by periodic outbursts of violence often pitting Uighurs against ethnic Han Chinese.
"They gave two reasons. The first was that it could hinder the investigation, and the second was that it involved state secrets," lawyer Li Fangping said by telephone from Urumqi.
In China's judicial system, courts answer to the ruling Communist Party, but it is rare to completely deny the accused, even a political dissident, access to counsel.
Any implication of access to state secrets adds a degree of severity to the charges and is also rare.
Li said that if authorities were worried about hindering the investigation, they would not have made details of the case public on an official microblog run by the Urumqi government, as happened last month, a week after Tohti's detention.
"Only if Ilham possessed documents with state secrets would the case involve state secrets," he said.
Li said he would submit a legal rebuttal and hoped the authorities would reconsider.
Tohti could face the death penalty, though Li said that he was most likely to receive a sentence of between 10 years and life in prison. Convictions are almost certain in Chinese courts.
Unrest in Xinjiang has killed more than 100 people in the past year, prompting authorities to toughen their stance. Many Uighurs resent restrictions on their culture and religion, though Beijing says it grants them broad freedoms.
Advocates for Tohti say he has challenged the government's version of several incidents involving Uighurs. That includes what China says was its first major suicide attack, in Beijing's Tiananmen Square in October, involving militants from Xinjiang, by pointing out inconsistencies in the official accounts.
The United States, European Union and international rights groups have demanded Tohti's release.
The U.S. State Department said on Wednesday it was "deeply concerned" about his arrest.
China's Foreign Ministry spokeswoman, Hua Chunying, called the U.S. statement "gross interference" in China's legal system.
"I want to emphasise that the law is sacred and inviolable. Punishing crime in accordance with the law is a country's sovereign right," Hua told a press briefing.
William Nee, a China researcher for Amnesty International, said the government's treatment of Tohti's case had been "highly irregular".
"It's very confusing in a way," Nee said. "If he's being charged with separatism, it's hard to understand how that would involve state secrets. I'm not sure what state secret he would have access to."
Tohti's wife, Guzaili Nu'er, maintains his innocence, saying that he has done nothing that could constitute separatism. She told Reuters on Wednesday that police were tailing her.
Tohti, who teaches at Beijing's Minzu University which specialises in ethnic minority studies, told Reuters in November that state security agents had threatened him for speaking to foreign reporters.
He has said that he has never associated with a terrorist organisation or a foreign-based group and has "relied only on pen and paper to diplomatically request the human rights, legal rights, and autonomous regional rights for the Uighurs". (Additional reporting and writing by Sui-Lee Wee; Editing by Ron Popeski)