A man has died after being hit in the head by a projectile during Hong Kong protests and a minister has been injured during a clash with demonstrators in London, as chaotic rallies paralysed the Chinese city for a fifth consecutive day on Friday.

Videos shared on social media showed an elderly street cleaner being hit on the head by what appeared to be a brick thrown by masked protesters.

Authorities said the 70-year-old died of his injuries on Thursday night. The Hong Kong government expressed outrage, calling it a “malicious act of the rioters”, and police said they were treating it as a murder investigation.

The Food and Environmental Hygiene Department expressed profound sadness at the death of one of its workers, and said it was providing assistance to his family.

It came one week after the first confirmed death in the clashes, a student protester who fell from the third floor of a multi-storey car park during a police dispersal operation. On Monday, a protester was shot in the abdomen by a police officer and a man arguing in support of Beijing was set on fire in the street.

Meanwhile, both the Chinese and devolved Hong Kong governments on Friday issued strong statements decrying an incident in the UK involving the Hong Kong justice secretary Teresa Cheng.

Ms Cheng was at an event in London on Thursday, promoting Hong Kong as a hub for dispute resolution and deal-making, when she was surrounded by a group of protesters shouting slogans such as “murderer” and “shameful”.

The justice secretary is an unpopular figure in her own right among the pro-democracy movement in Hong Kong, having played a key role in pushing forward chief executive Carrie Lam’s controversial extradition bill - one of the main triggers for the months-long unrest.

Video of the incident shows Ms Cheng falling as she tries to make her way through the crowd of protesters, before her security guards regain control of the situation.

The Chinese embassy in the UK said Ms Cheng was pushed, and that she had sustained an injury to her hand as she fell.

The Hong Kong government said she had suffered “serious bodily harm”, while Ms Lam called the incident a “barbaric” attack.

“[Ms 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.

Hong Kong protesters out in force after months of turmoil: In pictures Show all 32 1 /32 Hong Kong protesters out in force after months of turmoil: In pictures Hong Kong protesters out in force after months of turmoil: In pictures A protester throws a stone into a building at Hong Kong Polytechnic University on 11 November Reuters Hong Kong protesters out in force after months of turmoil: In pictures Police patrol the streets of Hong Kong the day after an officer shot a protester during a protest on 11 November EPA Hong Kong protesters out in force after months of turmoil: In pictures Riot police stand guard during a protest against police brutality in Hong Kong on 27 October EPA Hong Kong protesters out in force after months of turmoil: In pictures Protesters carry traffic cones to build a barricade during anti-government protests in Causeway Bay, Hong Kong on 11 November Reuters Hong Kong protesters out in force after months of turmoil: In pictures Protesters use obstacles and bricks to block a road in Hong Kong on 11 November AP Hong Kong protesters out in force after months of turmoil: In pictures Graffiti on a window smashed by student protesters in Hong Kong Polytechnic University AP Hong Kong protesters out in force after months of turmoil: In pictures Protesters carry US and British flags during a demonstration in Hong Kong on 11 November Reuters Hong Kong protesters out in force after months of turmoil: In pictures A protester throws a bottle of water as he is shrouded in tear gas during a demonstration in the Tsim Sha Tsui district of Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Journalists take pictures of police officers as they move to disperse protesters in Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures An man lies injured after being attacked by protesters who suspected him of being an undercover police officer on 27 October EPA Hong Kong protesters out in force after months of turmoil: In pictures A man runs among tear gas during a protest in Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Protesters gather on a field in the Tsim Sha Tsui district of Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Pro-democracy protesters turn away from a fire lit outside the Causeway Bay Mass Rapid Transit (MTR) station in Hong Kong on 4 October Getty Hong Kong protesters out in force after months of turmoil: In pictures People rest near rows of riot police officers during a protest in Mong Kok, Hong Kong on 27 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures Pro-democracy protesters hold umbrellas as police fire tear gas at them ouside Tai Koo MTR station in Hong Kong on 3 October Getty Hong Kong protesters out in force after months of turmoil: In pictures Hong Kong police fire a water cannon from the central government office at protesters during a mass rally on the 70th anniversary of the founding of communist China on October 1 AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Protesters burn a Chinese national flag during a mass rally on the 70th anniversary of the founding of communist China on 1 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Protesters remove signs celebrating the 70th anniversary of the founding of communist China during a mass rally in Hong Kong on 1 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Cardboard boxes set alight by protesters burn in the streets of Hong Kong during a mass rally on the 70th anniversary of the founding of communist China on 1 October EPA Hong Kong protesters out in force after months of turmoil: In pictures An anti-China banner has been placed in a barricade during a mass rally on the 70th anniversary of the founding of communist China on 1 October EPA Hong Kong protesters out in force after months of turmoil: In pictures A pro-democracy protester runs away after police fire a tear gas canister in Hong Kong's Wong Tai Sin district on October 4 Reuters Hong Kong protesters out in force after months of turmoil: In pictures Protesters run after police fire tear gas during a mass rally on the 70th anniversary of the founding of communist China on 4 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Pro-democracy protester take cover after police fire a tear gas canister in Hong Kong's Wong Tai Sin district on 4 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures The rally comes after months of protests on the streets of Hong Kong which began in oppposition to a proposed extradition bill EPA Hong Kong protesters out in force after months of turmoil: In pictures The extradition bill would have allowed the government to extradite people to China if they were facing certain criminal charges AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Opposition to the bill stems from the fear that the Chinese government would abuse this power for political or commercial reasons EPA Hong Kong protesters out in force after months of turmoil: In pictures Protesters soon came to demand greater freedom and universal suffrage under the One Country, Two Systems principle AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures Protesters are wearing black to symbolise opposition to China as they take to the streets in a "day of grief" while the Chinese state celebrates the 70th anniversary of its communist founding AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures A protester charges forward holding umbrellas as a mass rally breaks out in violence in Hong Kong on 1 October AFP/Getty Hong Kong protesters out in force after months of turmoil: In pictures A protester pours water on a tear gas canister fired by police during a mass rally on the 70th anniversary of the founding of communist China on 1 October Reuters Hong Kong protesters out in force after months of turmoil: In pictures A protester carries a vandalised Chinese flag through Hong Kong during a mass rally on the 70th anniversary of the founding of communist China on 1 October EPA Hong Kong protesters out in force after months of turmoil: In pictures Protesters carry a banner that denounces the celebration of the 70th anniversary of the founding of communist China on 1 October EPA

Beijing said it had lodged a formal complaint with the UK and urged British authorities to bring the perpetrators to justice.

It was the most direct physical confrontation between protesters and any senior members of Ms Lam’s administration since the demonstrations escalated in June. The pro-democracy movement is demanding the city’s civil liberties and autonomy be protected from perceived encroachment by Beijing.

Friday again saw a flash mob emerge in the central business district while office workers were on their lunch breaks.

City traders and businessmen and women wearing banned face masks chanted “Liberate Hong Kong, revolution of our time”, before returning to work.

The scenes of orderly but impassioned protesting in Central each day this working week show the protest movement continues to receive deep support from the general public, and run counter to the Chinese media narrative that paints all pro-democracy supporters as “rioters”.

A 31-year-old office worker who only gave her name as Nicole told the Reuters news agency: “Things that happened in these few months have made people heartbroken.

“The government only came out to condemn rioters ... They have never thought why so many rioters have emerged in our city and why ordinary citizens support them,” she said.

Hong Kong is due to hold local elections on 24 November, and opposition politicians have accused the authorities of deliberately intensifying clashes between police and protesters in order to build a pretence for cancelling the polls.