(CNN) A journalist working for Chinese state media was removed from a fringe event discussing Hong Kong at the UK Conservative Party conference on Sunday after loudly protesting a speaker.

The move sparked outrage from the Chinese Embassy to the UK, which said the journalist's ejection from the event in Birmingham was "completely unacceptable."

"In a country that boasts freedom of speech, it is puzzling that the Chinese journalist should encounter obstruction in such a way and even assault at the fringe event when she simply raised a question and expressed her opinions," the embassy said.

Chinese state broadcaster CCTV demanded an apology from UK authorities on Monday, confirming in a statement the journalist was an employee of the network named Kong Linlin.

CNN reached out to the journalist via social media but did not immediately receive a reply.

The event, held on the sidelines of the annual conference for the UK's ruling Conservative Party, was a discussion of "erosion of freedom" in the former British colony and current Chinese special administrative region (SAR) of Hong Kong. It was hosted by Conservative member of Parliament Fiona Bruce and featured several Hong Kong democracy advocates.

In a video of the event taken by conference attendee Adam Kerson, the female Chinese journalist suddenly began yelling during the event.

Conservative Party volunteer Enoch Lieu, 24, is shown in the video trying to calm the woman down and asking her to leave before she slaps his hand away.

She was then physically restrained by another attendee, who in the video is shown tightly gripping her arms while standing behind her. In response to the man placing his hands on her arms, she yelled "you have no right" and "leave me alone."

As she was being led out she yelled, "Oh how democratic, the UK!"

First day of #CPC18, managed to get slapped in the face twice, literally. I was helping in @CPHumanRights and @hk_watch fringe event on Hong Kong, a reporter from Chinese state-owned #CCTV shouted from her seat. When I asked her to leave, she refused and assaulted me pic.twitter.com/8BWi4hDfgU — Enoch Lieu (@enochcafe) September 30, 2018

Lieu told CNN that the woman had begun yelling during the closing remarks by UK human rights advocate Benedict Rogers, who told the audience he was "not anti-China."

"She stood up and shouted at them, 'You're a liar,' 'You're anti-China,' 'You're trying to separate China' (and) 'You're all puppets of the West,'" he said.

After her outburst, Lieu said he tried to ask the woman to leave but she refused and kept shouting. When Lieu insisted, he said she slapped him.

"The rest of the audience was completely stunned by what happened," he said.

Today I had privilege of speaking about the threats to Hong Kong's freedoms, autonomy and the rule of law, alongside three inspiring champions of human rights - Hong Kong's Martin Lee, Benny Tai and Nathan Law Kwun Chung, at the Conservative Party Conference in Birmingham #CPC18 pic.twitter.com/O15vqXIObp — Benedict Rogers (@benedictrogers) October 1, 2018

West Midlands Police said in a news release that a 48-year-old woman from London was arrested at the venue on suspicion of common assault and later released as the investigation continues.

In a statement, the Chinese Embassy said that Hong Kong's affairs "are purely China's domestic affairs," adding the organizer of the fringe event should apologize to the Chinese journalist.

"It was a cause for grave concern and strong objection. China firmly opposes interference in Hong Kong's internal affairs by anyone or any organization in any form," it said.