Six former members of staff at Hong Kong's defunct pro-democracy newspaper Apple Daily pleaded guilty on Tuesday to conspiracy to commit collusion with foreign forces in a closely watched national security case.

The six pleaded guilty to conspiring with media tycoon Jimmy Lai and other people to request a foreign country or organisation “to impose sanctions or blockade, or engage in other hostile activities” against the Hong Kong and Chinese governments between July 2020 and June 2021.

The six include Cheung Kim-hung, who was chief executive of the newspaper's former owner, Next Digital, Apple Daily's former associate publisher Chan Pui-man, former editor-in-chief Ryan Law, former executive editor-in-chief Lam Man-chung, former English edition editor-in-chief Fung Wai-kong and former editorial writer Yeung Ching-kee.

Prosecutor Anthony Chau said Apple Daily was used as a platform to advocate for foreign sanctions.

"The impugned content took the form of, among others, articles purported to be news coverage of current issues, commentary articles, and appeals or propaganda directly and unlawfully advocating political agenda," Chau said.

Chau also cited content published by Apple Daily as far back as March 2019, which he said included seditious statements and appeals to the public to take part in pro-democracy protests that year.

The 2019 protests were the biggest since the former British colony returned to Chinese rule in 1997 and were fueled by criticism from democracy campaigners who said Beijing had reneged on a commitment to maintain Hong Kong’s autonomy and freedoms under a “one country, two systems” formula.

Beijing and Hong Kong's government denied that and accused the protesters of undermining the stability at the heart of Hong Kong's economic success at the behest of foreigners.

Beijing imposed a security law in 2020 setting out punishment of up to life in prison for acts that China considers as subversion, secession, terrorism and collusion with foreign forces.

Lai and the six former Apple Daily staff members were charged with conspiracy to commit collusion with foreign forces under the law.

A fierce critic of Beijing, Lai, who is already in jail after being convicted for his role in an illegal assembly in 2020, faces multiple charges under the national security law.

Lai and his three companies have pleaded not guilty to the national security and sedition charges.

Some of the six will give evidence in Lai's trial, Chau said. Their sentences will be handed down at the end that trial, which will begin on Dec 1 and is expected to last 30 days.

- Reuters