Wong said the man was wearing white and a face mask and attacked him from behind, hitting his neck with double rattan canes. Men in white with canes had attacked commuters at Yuen Long mass transit railway (MTR) station in July as police stood by, in what was believed to be a hit organised by pro-Beijing groups.

Wong said the attack on him was "planned and organised". "I will never forgive myself for leaving Hong Kong at such a critical time," he wrote. But he said that to stay and continue his work at the student union would be putting his family in a dangerous position.

The High Court on Friday ruled that police cannot use the medical records of a woman hit in the eye during a protest - by what she alleges was a police beanbag round - until a judicial review is heard.

The woman has become an icon of the protest movement, featured on posters and inspiring protesters to hold a hand over one eye. Her injury, at Tsim Sha Shui on August 11, prompted angry student protesters to blockade the airport the next day.

Police have refused to reveal to her lawyers the content of a warrant used to obtain her medical records from hospital without her consent. Protesters have speculated police may use the medical records to lay charges against her for attending a protest.

The woman's lawyer told the court she has been subjected to doxxing - when online vigilantes publish a person's private information online - and cyber harassment.

In June, police entered hospitals and arrested patients who presented with beanbag and rubber bullet injuries, prompting an outcry from medical staff.

A teenager from the Carmel Pak U Christian secondary school was meanwhile reported to be tied to a hospital bed by one arm this week under police instructions. He received baton wounds to the head after his arrest at Tai Po train station.

Medical workers took out full-page newspaper advertisements to accuse police of torturing protesters during arrests and state the "inhuman behaviours of the police are damnable and despicable". The ads included the worker's names.

The High Court this week ruled a 20-year-old student charged with rioting should be allowed to leave Hong Kong to study in Poland because the police evidence against her was "not strong".

Protesters switched tactics this week and instead of taking to the streets gathered with thousands of office workers in shopping malls to sing Glory to Hong Kong, a new anthem.