Hong Kong police have fired tear gas at demonstrators during fresh clashes in the former British colony.

In a resumption of chaotic scenes which have been seen numerous times in the city this summer, protesters cut down a “smart lamppost” amid worries they contain surveillance devices for use by the Chinese government.

Demonstrators in Kowloon used an electric saw to slice through the bottom of one lamppost, while others pulled ropes tied around it.

The activists, who were holding up umbrellas to hide their identities, cheered as it toppled over.

They were part of a larger group marching to demand the removal of the lampposts over worries they could contain high-tech cameras and facial recognition software used for surveillance by authorities.

The government in Hong Kong, which has been convulsed by more than two months of sometimes violent protests, said smart lampposts only collect data on traffic, weather and air quality.

The semi-autonomous Chinese city has said it plans to install about 400 of the smart lampposts in four urban districts, starting with 50 this summer in the Kwun Tong and Kowloon Bay regions which were the scene of Saturday’s protest march.

Petrol bombs were hurled at riot police Credit: AP

Organiser Ventus Lau said ahead of the procession: “Hong Kong people’s private information is already being extradited to China. We have to be very concerned.”

Police fired tear gas for the first time in more than a week after black-clad protesters set up makeshift barricades on a road outside a police station.

Officers used minimum force to disperse the protesters after repeated warnings became “futile”, the government said in a statement.

Protesters threw bricks and petrol bombs as police chased them down a main road.

The protest march had started peacefully as supporters chanted slogans calling for the government to answer the movement’s demands.

Demonstrators run from riot police as protests flared up again for the first time in a week Credit: AP

Demonstrations began in June with calls to drop an extradition bill that would have allowed Hong Kong residents to be sent to China to stand trial. The protests widened to include calls for free elections to the post of the city’s chief executive and an independent inquiry into alleged police brutality.

Hong Kong’s government-owned subway system operator, MTR, shut down stations and suspended train service near the protest route, after Chinese state media accused it of helping protesters flee in previous protests.

MTR said on Friday that it may close stations near protests under high risk or emergency situations.

The company has until now kept stations open and trains running even when there have been chaotic skirmishes between protesters and police.

Mr Lau said MTR was working with the government to “suppress freedom of expression”.

It is the latest outbreak of violence during a summer of unrest in the semi-autonomous Chinese region Credit: AP

Also on Saturday, Chinese police said they released an employee at the British Consulate in Hong Kong as scheduled after 15 days of administrative detention.

Simon Cheng Man-kit was detained for violating mainland Chinese law and “confessed to his illegal acts,” the public security bureau in Luohu, Shenzhen, said on its Weibo microblog account.

The Chinese government has said that Mr Cheng, who went missing after travelling by train to mainland China for a business trip, was held for violating public order regulations in Shenzhen, in a case that further stoked tensions in Hong Kong, a former British colony.

The British government confirmed his release.

A protester throws a missile at police Credit: AP

“We welcome the release of Simon Cheng and are delighted that he can be reunited with his family,” the Foreign and Commonwealth Office said in a statement, adding that Mr Cheng and his family had requested privacy.

The Scottish Government trade and investment officer was a local employee without a diplomatic passport.

The Global Times, a Communist Party-owned nationalistic tabloid, said on Thursday he was detained for “soliciting prostitutes”.

China often uses public order charges against political targets, and has sometimes used the accusation of soliciting prostitution.