Hong Kong leader Carrie Lam said on Tuesday the government was working on "fake news" legislation to tackle "misinformation, hatred and lies," as worries grow over media freedoms in the global financial hub.

Under Beijing's directions, Hong Kong has taken a swift authoritarian turn following the imposition of a sweeping national security law in 2020, with a fresh drive for "patriotism" spilling into most aspects of life in the city.

A major overhaul of public broadcaster RTHK, led by a newly appointed bureaucrat with no media experience, is widely seen as a signal that government red lines will soon encircle journalism as they have other sectors, such as education.

Speaking at her weekly news conference, Lam said the government was researching "fake news", but added she had no timetable for the legislation.

"The fake news law needs a lot of research, especially (on) how overseas governments are tackling this increasingly worrying trend of spreading inaccurate information, misinformation, hatred and lies on the social media," she said.

"We will continue to be very serious about this issue because of the damage it is doing to many people."

Her comments come a day after RTHK reported the broadcaster would not renew the contract of its journalist Nabela Qoser, known for her tough questioning of Lam and other officials during mass 2019 anti-government protests.

RTHK has also begun removing some of its archives from its Youtube and social media channels, prompting online activists to back up some of the content on blockchain platforms.

Another RTHK journalist, Bao Choy, was found guilty by a court last month of improperly accessing public records for a documentary on the police handling of a mob attack on pro-democracy protesters, reporters and bystanders in 2019.

Her documentary won a local press award the day before the verdict, which RTHK did not accept.

The July 2019 attack in northern Yuen Long district, when more than 100 men in white T-shirts hit people with sticks and poles at a train station, sparked widespread criticism of the police including allegations of collusion with triad gangsters, which police deny.

Courts have yet to convict any of the attackers.

Reporters Without Borders ranks Hong Kong 80th out of 180 in terms of press freedom, in freefall over the past decade.