The Chinese Central and Hong Kong Special Administrative Region (HKSAR) governments condemned on Friday an attack by a "violent mob" on Hong Kong's justice secretary in London, the first direct assault by demonstrators against a government minister during months of often violent protests.

Teresa Cheng, secretary for justice, who was in London to promote Hong Kong as a dispute-resolution and deal-making hub, was targeted by a group of protesters who shouted "murderer" and "shameful."

A statement by the Hong Kong SAR government said Cheng suffered "serious bodily harm," but gave no details.

The Chinese embassy in the UK said Cheng was pushed to the ground and sustained a hand injury.

"[Cheng)] was besieged and attacked by dozens of anti-China and pro-independence activists," the Chinese embassy said in a statement. The incident showed that the "violent and lawless perpetrators" were now taking their violence abroad, it said.

In a statement, the Chinese ambassador to the UK, Liu Xiaoming, extended sympathy on behalf of the Central Government and said the actions would not only be condemned by Chinese people, including Hong Kong residents, but would also be condemned by the British people and the international community.

Also in the embassy's statement, Cheng thanked the leaders of the central government and the State Council for their concern and support. It said she would continue to assist the Hong Kong chief executive and the SAR Government in stopping the violence, restoring order and better implementing "One Country, Two Systems."

China has lodged a formal complaint with Britain and urged British authorities to bring the perpetrators to justice. 

In a press briefing, Chinese Foreign Ministry spokesperson Geng Shuang pressed the UK government for action: "We demand the UK to immediately investigate the incident, do their best to arrest the perpetrators and bring them to justice." 

Adding: "The UK should protect the safety and dignity of all Chinese personnel in the country. We urge the British side to exercise prudence on Hong Kong-related issues, to stop sending wrong signals, stop inciting chaos and stop meddling in Hong Kong affairs and China's internal affairs."

Hong Kong's leader Carrie Lam also strongly condemned the attack.

The SAR government said in a separate statement: "The secretary denounces all forms of violence and radicalism depriving others' legitimate rights in the pretext of pursuing their political ideals, which would never be in the interest of Hong Kong and any civilized society."

A 70-year-old street cleaner, who videos on social media showed had been hit in the head by a brick thrown by "masked rioters" died on Thursday, authorities said.

The protests escalated in June over a now-scrapped fugitive bill that would have allowed alleged perpetrators to be sent to other parts of China including the mainland, Macao and Taiwan for trial. 

In a statement, the London's Metropolitan Police said: "Police are investigating an allegation of assault in Bury Place, Camden WC1 at around 17:05hrs on Thursday, 14 November.

"A woman was taken to hospital by London Ambulance Service suffering an injury to her arm. Enquiries are ongoing to establish the full circumstances. There has been no arrest at this stage."

With Reuters