Two friends of Yang, the U.S.-based publisher Shi Wei and Feng Chongyi, a professor at the University of Technology Sydney, told The Washington Post the writer took off from New York on a China Southern Airlines flight for Guangzhou but fell out of touch after he landed early Saturday.
Yang's wife, who was traveling with him and their two children, told friends that she was questioned in Guangzhou and her husband had been detained by state security, according to Feng.
Yang's wife later also fell out of contact but not before she sent friends a picture of the Beijing airport without explanation on Sunday. The picture signalled that she felt compelled to travel to the Chinese capital but could not say why, Feng said.
Supporters say Yang has been an outspoken writer who has been a thorn in the government's side for more than a decade but traveled unhindered to China, as recently as several months ago.
Something changed in the last few months to prompt his alleged detention.
"My judgment is this is linked directly to the Huawei case," said Feng, referring to the possibility that China is taking a harder line against citizens of countries aligned with the United States.
This is not the first time that Yang has been held in China, which he left in the 1990s following a stint at China's Foreign Ministry.
For years, Yang publicly joked that he was frequently recruited to be an asset for foreign intelligence. He wrote spy novels about China and the United States as well as criticism of Chinese politics that was seen in intellectual circles as unvarnished yet relatively moderate.
After he was detained in 2011, also during a trip to Guangzhou, Yang declined to publicly discuss the experience. But he wrote in a blog post that he would continue to work as a "calm intermediary" who pushed China - "our nation" - to become a strong, prosperous, free and democratic country.
In the past six months, relations between Beijing and U.S. allies have soured dramatically over duelling allegations of politically motivated arrests. China has viewed the international backlash against Huawei, including Canada's seizure of Meng, as a campaign orchestrated by the United States to undermine a symbol of corporate China's international success. It has warned Western capitals against siding with Washington - or else face severe consequences.
"We need to select counter-targets and make those countries be beaten very painfully. We argue that in this complex game, China should focus on the Five Eye alliance countries, especially Australia, New Zealand, and Canada," the Communist Party-run newspaper Global Times said in a December commentary. "They follow the United States to harm China's interests."
Australia, which has maintains important trade ties with China, defied Chinese warnings this month and sided with Western allies in a statement that expressed concern about China's detention of the two Canadians.
Australian national security officials have mostly echoed their U.S. counterparts, issuing warnings about the security risks of Huawei participating in the country's telecom infrastructure.
After Australia and New Zealand banned Huawei from building their domestic 5G networks last autumn, Huawei chairman Guo Ping criticized unspecified countries for their "incredibly unfair" and "malicious" treatment of his company.
