China's plan to impose national security laws on Hong Kong could have serious implications for civil liberties and press freedom, rights groups say.

Hong Kong's government on Friday said it would work with Beijing to enact the law, which seeks to ban "secession, subversion or terrorism activities."

Carrie Lam, Hong Kong's chief executive, said the plans would not affect rights, freedoms or judicial independence.

Rights groups, however, warned that the law could be used to suppress the media.

'Tiptoeing'

"Already, journalists are expressing fear that interviewing the wrong person or reporting controversial views could land them in trouble. The result would be an increase in self-censorship," Steven Butler, head of the Asia program at the Committee to Protect Journalists (CPJ), said.

"Journalists had already been tiptoeing around controversial topics, such as Hong Kong independence," he said. "The new laws promise to widen the zone of uncertainty about what is permissible and stokes fears that mainland Chinese-style censorship could be on the way."

Human Rights Watch described the law as "the most severe blow to the rights of people in Hong Kong since the territory's transfer to China in 1997."

"Hong Kong people will now have to consider arrests and harsh sentences for protesting, speaking out, running for office and other freedoms they have long enjoyed and struggled peacefully to defend," Sophie Richardson, the group's China director, said in a statement.

Selina Cheng, a reporter for a Chinese-language news outlet in Hong Kong, told VOA last month that journalism had already become more challenging since mass anti-government protests began last June.

"There's been a constant infringement on press freedom when it comes to dealing with the police in Hong Kong, especially when it comes to protest coverage," Cheng said. "It seems like the circle of what people can report on freely has narrowed down."

China has previously used anti-state accusations to retaliate against critical journalists, CPJ data show.

Jailer of journalists

The country is the world's worst jailer of journalists, with 48 behind bars at the time of CPJ's last prison census.

The country also ranks 177th out of 180 countries, where No. 1 is the most free, according to the World Press Freedom Index by Reporters Without Borders.

Rick Dunham, from the global business journalism program at Tsinghua University, Beijing, described conditions for the press in China as challenging.

"It sometimes is complicated for journalists to report on sensitive stories," he said last month, citing issues including Taiwan, protests in Hong Kong and the Uighurs as areas that Beijing is particularly sensitive to.

Dunham said that while other countries, such as Mexico, were more dangerous for journalists, "in China, the risk is you lose your freedom."

Some information for this report came from Reuters.