BEIJING (Reuters) - China jailed a Tibetan businessman for five years on Tuesday for “inciting separatism”, his lawyer said, after he advocated the use of Tibetan in schools and was featured in international media reports.

Liang Xiaojun, one of his lawyers, said Tashi Wangchuk was handed a five-year prison sentence but declined to give further details.

The U.S. State Department said it was “deeply disappointed” by the verdict and that Tashi was “exercising his fundamental freedom of expression in calling on the government to give greater attention and resources to teach the Tibetan language in Tibetan areas.”

“We urge Chinese authorities to release Tashi Wangchuk immediately and to protect the distinct religious, cultural and linguistic identity of Tibetans,” State Department spokeswoman Heather Nauert said in a statement.

Tashi appeared in a New York Times video in January 2016 in which he spoke about his efforts to protect the right of Tibetans to attend school taught in their mother tongue.

In the report, he also traveled to Beijing to seek an audience with the central government and told the Times that he was not calling for Tibetan independence.

Chinese troops entered predominantly Buddhist Tibet in 1950 in what Beijing says was a peaceful liberation of the region. It says it brought prosperity and freedom to what was a backward and feudal society, including freeing a million people from serfdom.

During a trial in January in northwest China’s Yushu prefecture in Qinghai province, the Times’ video report was heavily cited as evidence for the charges of inciting separatism brought against Tashi, his lawyers said at the time.

Liang said on Twitter, which is banned in China, that he was unable to give interviews to foreign media as his law firm was under yearly review by China’s legal authorities but that he maintained his belief in Tashi’s innocence.

A person who answered the phone at the Yushu Intermediate People’s Court said that they were unaware of the case.

China maintains that it protects the rights of all ethnic minority cultures and its constitution grants groups the freedom to use and develop their own written and spoken languages.

But rights groups say that the government drive to popularize standardized Mandarin Chinese erodes the languages used by minorities such as Tibetans and that Beijing is essentially forcing cultural assimilation.

Joshua Rosenzweig, East Asia Research Director at Amnesty International, said the verdict and sentence were a “gross” injustice.

“He is being cruelly punished for peacefully drawing attention to the systematic erosion of Tibetan culture. To brand peaceful activism for Tibetan language as ‘inciting separatism’ is beyond absurd,” he said in a statement.

There have been sporadic protests against Chinese rule in Tibetan parts of China for the past few years, most seriously in 2008 ahead of the Beijing Summer Olympics.

Beijing calls Tibetan spiritual leader the Dalai Lama a dangerous reactionary who seeks to split off nearly a quarter of the land mass of the People’s Republic of China.

The 1989 Nobel Peace laureate, who fled Tibet into exile in India in 1959, denies the charge and says he seeks greater rights, including religious freedom and autonomy, for Tibetans.