The violent attack on a Global Times reporter at Hong Kong International Airport on Tuesday ignited condemnation from the international community.

"I saw the entire footage and could not believe what the rioters did to Fu Guohao, a Chinese civilian who was legally doing his job," said Ben Zhang, a San Francisco Bay Area resident. "The protesters were so brutal, irrational and inhumane. What an irony that it's this group of people who have been vocalizing their so-called pursuit of the rule of law."

Violent activists bound the hands of Fu and accused him of posing as a reporter. They beat him, "leading to multiple injuries", according to a statement from the Hong Kong and Macao Affairs Office of the State Council.

Any violence or breach of the law is unacceptable, said Li Fu, an engineering professor at Portland State University in the US state of Oregon.

"The stability and prosperity of Hong Kong is not only in the interests of the local people, but also serves the well-being of China and the world," he added.

"If protestors occupied the main Washington airport, shut down all flights and beat up police and reporters, the United States government would send in the Army National Guard and be cheered by the mainstream media. But apparently such lawlessness is okay if done in Hong Kong. US hypocrisy knows no bounds," said Reese Erlich, author of five books on US foreign policy.

"It's disgusting many who claim the HK police are tyrants for allegedly targeting media are apologists saying it's ok for rioters to target a Global Times reporter because he reports for the other side. These rioters are endangering natl security." Shaun Rein, the founder and managing director of China Market Research Group, posted on Twitter on Tuesday.

Loizos Heracleous, chairholder in strategy and organization at Warwick Business School, said: "While peaceful protests are desirable, crossing the line into violence by any side is not because it can escalate things toward very undesirable territory."

"The situation in Hong Kong has now become risky in terms of potential consequences, but also threatens the reputation of the city as a safe and stable business hub served by a world class airport," Heracleous said.

"I hope the violent behavior will stop, dialogue will resume, peace and quiet will return and Hong Kong will carry on as a key financial and economic hub and vibrant metropolis so loved around the world," said Eugenio Bregolat, former Spanish ambassador to China.

Edith Mutethya in Kenya and Chen Weihua in Brussels contributed to the story.