Kong said that the girl was not arrested during recent protests and that there was no wound or any sign of sexual assault on her body, but that the cause of death was still to be confirmed.

He said surveillance footage from the girl’s school showed she left her possessions on the campus before walking barefoot towards the waterfront near Tseung Kwan O on September 19. She was reported missing two days later and her body was found on September 22, he said.

But some protesters were not convinced, and used candles to form the Chinese characters for “truth” as they remembered the teenager at the Hong Kong Design Institute in Tseung Kwan O.

At a so-called citizens’ press conference on Friday, a protester, who did not give his real name, said the public could not trust the police’s account of the incident.

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“Recent cases of death including the 15-year-old girl leave us with many questions, whether they really fell into the sea and killed themselves, or died an unnatural death,” he said.

Elsewhere, there were peaceful protests in a Sha Tin shopping centre, at Ma On Shan and in the Elements mall in West Kowloon. About 50 demonstrators also gathered outside the Heung Yee Kuk Building in Sha Tin as Hong Kong’s embattled leader, Chief Executive Carrie Lam Cheng Yuet-ngor, as well as Wang Zhimin, head of Beijing’s liaison office in the city, attended a closed-door function.

“Liberate Hong Kong, revolution of our times! Lam, come and talk to us!” they shouted as the chief executive left in a car.

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In Tai Po, protesters formed a human chain from Kwong Fuk Road, crossing a tunnel under Po Heung Bridge, to On Chee Road. Many turned on the flashlights on their cellphones and chanted slogans. “No more delay to dismissing the police force!” they shouted.

The crowds on Friday were smaller than a week ago, when radicals rampaged across Hong Kong and vandalised shops and public facilities such as MTR train stations in protest against a ban on the wearing of masks at public assemblies.

Those who gathered in Central and Tai Po said they were protesting against alleged police brutality and the case of a Chinese University student, Sonia Ng, who claimed a policeman had hit her breasts after she was arrested on August 31 and detained. Police said on Friday that they would investigate Ng’s allegations.

A 24-year-old teacher named Kara who joined the Tai Po human chain said it was inappropriate for police to ask Ng to file a complaint.

“It would be dealing a second round of damage to ask someone to recount how she was subjected to sexual violence in front of others,” she said.

In the Elements mall in West Kowloon, about 10 secondary school students, most of them masked, brought instruments such as violins and flutes to play the popular protest anthem Glory to Hong Kong, and sang Do You Hear the People Sing in a flashmob protest.

“Hongkongers, resist!” they shouted.

Messages have been circulating on the internet calling for people to protest in places such as Tsim Sha Tsui, Sha Tin and Causeway Bay on Saturday and Sunday.

Meanwhile, an online survey by a group of anti-government protesters found that an overwhelming majority of Hongkongers were united against the new anti-mask law, which took effect on October 5.

The survey, based on questionnaires completed by more than 110,000 people via Telegram groups, Facebook and email on October 5 and 6, showed that 90 per cent of respondents opposed the ban on facial coverings and believed the law would aggravate alleged police misconduct.

Some 60 per cent said the government would use the Emergency Regulations Ordinance to further clamp down on protests, including longer detention for arrested people before trial and cancelling the upcoming district council elections due to take place in November.

A masked man at the citizen’s press conference said “the results showed protesters of all factions still stand resolutely behind the movement, especially after the passage of the anti-mask law”.

He added the results were significant as more respondents identified as moderate protesters. On a 10-point scale with zero being the most moderate, respondents gave a score of 4.87 on average, down from 5.15 in a September 8 survey.

Additional reporting by Victor Ting and Karen Zhang