HONG KONG (REUTERS, BLOOMBERG) - The Chinese and Hong Kong governments condemned on Friday (Nov 15) an attack by a "violent mob" on the city's Justice Secretary in London, the first direct altercation between demonstrators and a government minister during months of often violent protests.

Secretary for Justice Teresa Cheng, 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 government said Ms Cheng suffered "serious bodily harm" but gave no details. Video footage of the incident showed Ms Cheng falling to the ground.

Hong Kong's leader, Mrs Carrie Lam, said in a statement she strongly condemned what she described as an attack on Ms Cheng.

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

The Chinese embassy in Britain has urged British police to carry out a thorough investigation of the incident and to step up security for its personnel and organisations in Britain.

The incident came amid escalating violence in Chinese-ruled Hong Kong, where a student protester died earlier this month after falling from a parking lot during demonstrations.

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

Hong Kong's Food and Environmental Hygiene Department confirmed that one of its contract workers died on Thursday from a head injury, and expressed "profound sadness" over his death.

The 70-year-old worker "was suspected to be hit in his head by hard objects hurled by rioters during his lunch break", the agency said in a statement, adding that it would provide assistance to the victim's family.

Anti-government protesters paralysed parts of Hong Kong for a fifth day on Friday, forcing schools to close and blocking some highways as students built barricades on university campuses and the authorities struggled to tame the violence.

Protesters used barriers and other debris to block the Cross-Harbour Tunnel that links Hong Kong island to Kowloon district, leading to severe traffic congestion.

Service between Fo Tan and Lo Wu and Lok Ma Chau on the East Rail Line are suspended due to vandalism, railway operator MTR Corp said on Friday. Trains between Hung Hom and Fo Tan on the same line are running every five minutes. Stations at Mong Kok, Tseung Kwan O, Sai Wan Ho, Tuen Mun and Tung Chung also remain shut.

The government once again urged employers to adopt flexible working arrangements amid the chaos.

Thousands of students remain hunkered down at several universities, surrounded by piles of food, bricks, petrol bombs, catapults and other homemade weapons.

Police said the prestigious Chinese University had "become a manufacturing base for petrol bombs" and the students' actions were "another step closer to terrorism".

Around 4,000 people, aged between 12 and 83, have been arrested since the unrest escalated in June.

The demonstrations have paralysed parts of the city and battered the retail and tourism sectors, with widespread disruptions across the financial centre and no end in sight to the violence and vandalism.

A 15-year-old boy who suffered a head injury from what local media said may have been a tear gas canister was still in Tuen Mun Hospital, the Hospital Authority said. The agency said the boy's family asked that details of his condition - which was originally listed as critical - not be disclosed.

Six people, aged 17 to 62, had been admitted to various hospitals for treatment for protest-related injuries overnight. As of Friday morning, all are in stable condition.

The man shot by police in Sai Wan Ho on Monday is now in stable condition in Eastern Hospital. A man set on fire during an argument with protesters on the same day is still in critical condition at Prince of Wales Hospital.

Meanwhile, another protester group at the Chinese University of Hong Kong offered to remove barricades from the Tolo Highway in exchange for a government pledge to follow through with plans for District Council elections on Nov 24, according to Radio Television Hong Kong. Students had already reopened one lane in each direction, the South China Morning Post said.

During a visit to Brazil on Thursday, Chinese President Xi Jinping said "continuing radical violent crimes" in Hong Kong have "seriously trampled on the rule of law" and that "stopping the violence and restoring order" is the city's "most urgent task" at present.

The violence has "seriously challenged the baseline principle of 'one country two systems'," he said at a summit of Brics countries in the Brazilian capital of Brasilia.

The rare comments by Mr Xi came as the United States Senate moved to expedite passage of legislation that would support Hong Kong's pro-democracy protesters.

The Hong Kong government also dismissed speculation that it would impose a weekend curfew. China's state-owned Global Times newspaper had deleted a tweet that reported that the city's authorities were gearing up to announce widespread restrictions.

Hong Kong on Friday is expected to unveil the depth of its recession. Preliminary figures in October showed that the ruled city's economy shrank by 3.2 per cent in July-September from the preceding period, contracting for a second straight quarter and meeting the technical definition of a recession.

With no end to the increasingly violent protests in sight, analysts say the slump could be long and deep, with gross domestic product seen shrinking further this quarter and well into next year.

The protests, which have raged for more than five months, flared anew last week after the death of student, who fell near a police operation to clear a demonstration.

A campaign to disrupt traffic has led to the shooting of a protester and citywide school cancellations, while Chief Executive Lam's government has denied reports of a plan to institute an unprecedented curfew in a bid to quell unrest.

Meanwhile, the US Senate is preparing for quick passage of legislation that would support pro-democracy protesters by placing Hong Kong's special trading status with the US under annual review.

The Senate will run the "hotline" on the Bill, which is an expedited process to check for last-minute opposition to bringing legislation immediately to a vote, according to Senator Marco Rubio, a Florida Republican.

The Senate legislation is different than a version passed earlier by the House of Representatives. That means the two Bills would have to be reconciled and passed by both chambers before going to President Donald Trump to be signed into law.