China denied entry to a prominent US scholar of Tibetan issues, he said Monday, after he advocated on behalf of a detained Chinese minority academic.

Elliot Sperling, of the University of Indiana, was ordered to return home shortly after arriving at Beijing's international airport this weekend despite having a valid visa for entry, he told AFP.

Several US-based scholars researching Chinese politics and its policies towards ethnic minorities have been barred from entering China in recent years, but they are generally denied visas rather than being turned away.

Sperling said he was not given any explanation for the denial, but suspects that it was linked to his public support for Ilham Tohti, a scholar from China's mostly-Muslim Uighur minority, who was detained in January and charged with "separatism".

Tohti's arrest sparked concern from the US and the EU, as well as condemnation from international rights groups such as UK-based Amnesty International, who called him a "prisoner of conscience".

"The charges are clearly trumped up, he's one of the only Uighur intellectuals who doesn't entertain the idea of independence," Sperling said.

Sperling said he was detained for around an hour before airport staff escorted him directly onto a return flight.

"In reality I had paid for a one hour tour of China, a tour of the airport detention room," he added.

Authorities in Beijing could not be immediately reached for comment.

China's denial of visas to several prominent US-based China scholars has led to concerns that the prospect of being banned from the country could impact scholarship and limit academic freedom.

Most notably, 13 US-based scholars were denied entry to China after contributing chapters to a book published in 2004 about the far western region of Xinjiang, home to the Uighur minority.

The region has been hit by clashes between Uighurs and security forces, as well as several recent attacks on civilians which Beijing blames on separatists from the region.