(CNN) A public relations disaster for United Airlines is transforming into an international incident in one of its most important markets.

The man, who has not yet been identified, was overheard saying he was being profiled for being Chinese, a passenger told CNN, before police officers forcibly removed him from his seat on the overbooked flight.

'Discrimination'

The incident, which unfolded on Sunday, was the number one trending topic Tuesday on Weibo, China's answer to Twitter, attracting more than 100 million views.

Many commenters called for a boycott of United, accusing the airline of discriminating against the passenger because he is Chinese.

"It's straight up discrimination," one widely shared post said, while another commenter said they would never "fly with United again in my lifetime."

Joe Wong, a Chinese-born comedian who has performed multiple times on the "Late Show with David Letterman," said on Weibo "many Chinese people feel they've been subject to discrimination."

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"They stay silent because they fear losing face," he said. "That's why the Western mainstream media and public don't take discrimination against Asians seriously."

China is the second largest aviation market in the world and a key focus for United, which claims it "operates more nonstop US-China flights, and to more cities in China, than any other airline."

Representatives for United in China did not immediately respond to a request for comment.

Comedian Joe Wong was among many Chinese commenters on social media denouncing United's treatment of an Asian passenger. Wong denounced the airline for "discrimination" against Asians.

Forcibly removed

In a statement, the airline said four crew members needed to get to a flight departing from Louisville otherwise it would be canceled. Passengers on the Chicago-Louisville plane were asked to give up their seats voluntarily.

When no one volunteered, the airline was forced into an "involuntary de-boarding situation," airline spokesman Charlie Hobart told CNN. Four passengers were selected, including the man in the video. United denied accusations the man was chosen based on his ethnicity.

The man refused, saying he was a doctor and needed to see patients. The airline said it then followed US Department of Transportation protocol in calling local law enforcement to forcibly remove the man from the plane after he refused to disembark.

The Chicago Department of Aviation said in a statement that the incident "was not in accordance with our standard operating procedure and the actions of the aviation security officer are obviously not condoned by the department."

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PR disaster

The incident, which quickly went viral in the US and other countries as well as China, has become a public relations nightmare for United

Following a concentrated backlash on social media, United CEO Oscar Munoz issued a statement calling the incident "upsetting" and apologized "for having to re-accommodate" customers.

Ed Zitron , a PR expert and author of "This Is How You Pitch," said United's response to the incident "was a classic case of a company too afraid to make a categorical statement of compassion for fear of a lawsuit."

"Had United shown compassion and intent to make things right, they could have come out of this at the very least looking like an airline that cares. Instead they've just made it even worse," he said.