BEIJING — When Elliot Sperling, an American professor, landed here in Beijing after a 12-hour flight from the New York area last weekend, he found himself dragged by border officers into a back room in the airport for an interrogation. They then marched him back to the same United Airlines jet that he had flown in on, despite the fact he had arrived with a valid one-year tourist visa.

Mr. Sperling said he believed he was being punished for his vocal support of Ilham Tohti, an ethnic Uighur economics professor here who has beencharged by the Chinese authorities with separatism, and whose arrest has ignited outrage across the globe.

The forced removal of Mr. Sperling and cancellation of his visa is the clearest sign yet that China is desperate to silence international advocates of Mr. Tohti, a moderate scholar whose arrest has been denounced by the United States State Department, human rights groups and many others. In May,the PEN American Center, which defends freedom of speech, gave Mr. Tohti a prominent award; his daughter, Jewher Ilham, accepted it in his absence.

China increasingly uses denial of entry as punishment against scholars, journalists and others who write or speak in ways that Chinese officials deem politically offensive. The tactic has led to growing concern that intellectuals might censor themselves in order to maintain access to China, and some Americans have been calling for the United States to pressure China to back off. Mr. Sperling’s removal took place as senior American officials were arriving in Beijing to negotiate with the Chinese on various issues as part of the United States-China Strategic and Economic Dialogue.

“The issue for me is not my being denied entry — I can certainly continue my research and academic work without going to China — but the attempt to pressure those who speak in support of Ilham to retreat into silence, or at least to isolate them,” Mr. Sperling said.

Mr. Sperling, 63, who teaches Tibetan history at Indiana University, had arranged earlier for Mr. Tohti to spend one year as a visiting scholar at the university, which has a department of Central Eurasian studies. The two had become friends after meeting here in 2012. But Mr. Tohti was detained by police officers in February 2013 when he arrived at Beijing Capital International Airport to board his flight to the United States. His daughter, who was accompanying him, did board the flight and is now studying at Indiana University.

Mr. Tohti was formally charged with separatism in February. Ethnic and political tensions between Uighurs and the ruling ethnic Han have risen sharply in recent years, and violent clashes often flare now in the western frontier region of Xinjiang, the Uighur homeland. Mr. Tohti has promoted dialogue between Uighurs and Han, and has never advocated Uighur independence, Mr. Sperling said.

It was at the same airport where Mr. Tohti was detained in 2013 that Mr. Sperling ran into trouble on Saturday, after a direct flight from Newark. He had recently received a one-year tourist visa from the Chinese Consulate in Chicago, but border officers at the airport canceled the visa after pulling him from an entry line and questioning him for more than an hour in a small room. At one point, an officer took photographs of Mr. Sperling standing next to a height measurement chart, as if for a police mug shot.

Mr. Sperling’s tourist visa, which was valid until June 18, 2015, now has the word “canceled” stamped atop it in blue ink. Officers also scrawled a black X across the visa.

“I call it my Chinese Communist Party Human Rights Award,” Mr. Sperling said.

“There was obviously an order about me entered into the database,” he added. “I saw no point in arguing. I mean, I had a pretty clear notion about why I was being denied entry. For me, it was clearly about Ilham.”

When asked on Monday about Mr. Sperling’s case, a police officer surnamed Cheng who had answered the telephone at the visa office of the Public Security Bureau said he had not heard of it. A Foreign Ministry employee at the ministry’s press center also said she had no information.

The United States Embassy in Beijing declined to comment.

Mr. Sperling said he did not believe his scholarship on Tibet, also a delicate issue for the Chinese government, was the main factor. Until now, Mr. Sperling had traveled often to China on tourist visas. He made a trip in 2010 at the invitation of Chinese scholars hosting a private conference on Tibet. In 2011, Mr. Sperling came to here on a work visa to take up a post of about four months as a visiting scholar at Peking University. During that period, he gave academic lectures on Tibet around Beijing, including at Renmin University and at the Chinese Academy of Social Sciences.

Mr. Sperling is the latest Western scholar to join a list of academics denied access to China. Perry Link and Andrew J. Nathan, two professors in the United States who coedited “The Tiananmen Papers,” an inside look at the 1989 Tiananmen Square crackdown and massacre, cannot get visas to enter China. Orville Schell, who also worked on the book, can get visas only for brief visits.

Most notably, 13 scholars who contributed to a 2004 anthology on Xinjiang were put on a Chinese visa blacklist. Only about four or five have managed to get a Chinese visa in recent years.

One of the authors, Gardner Bovingdon, is a colleague of Mr. Sperling in the department of Central Eurasian studies at Indiana University. In May 2013, he received a Chinese visa after friends lobbied Chinese officials on his behalf. He landed in Beijing a month later, but was turned away by border officers at the airport in the same manner in which Mr. Sperling was rejected on Saturday, Mr. Bovingdon said in a telephone interview from Kazakhstan, where he has been doing research during his long ban from China.

Mr. Bovingdon said he believed his denial was not directly related to Indiana University’s ties to Mr. Tohti, but rather to the blacklist that resulted from the Xinjiang anthology.

More recently, China has aggressively put journalists and entire news organizations on visa blacklists to try to quash reporting on sensitive issues. Officials recently denied visas for two longtime resident journalists, Paul Mooney of Reuters and Melissa Chan of Al Jazeera English, forcing them to leave Beijing. China has also refused for two years to issue new resident visas for The New York Times and Bloomberg News, which published stories in 2012 on the hidden wealth of Chinese leaders’ families.

Mr. Sperling visited China just last year on a tourist visa, but said he did not know when he would be able to return.

“I don’t know if there is any way to get off the blacklist, but I see no reason to change my behavior,” he said. “I have done nothing wrong except to dissent — vociferously, I admit, but still I use only words — and have no intention of conforming to authoritarian norms for the sake of a visa.”