Six former senior executives of Hong Kong's now-defunct Apple Daily newspaper pleaded guilty on Tuesday to conspiring with newspaper founder Jimmy Lai Chee-ying to collude with foreign or external forces to endanger national security.

The three-judge panel accepted the guilty pleas and recorded the convictions.

The prosecution revealed that some of the six defendants will testify in the upcoming trial against Lai, which is scheduled to begin on Dec 1.

The sentencing of the six was adjourned until after the completion of Lai's case.

The six defendants are former editor-in-chief Ryan Law Wai-kwong, former publisher Cheung Kim-hung, former executive editor-in-chief Lam Man-chung, former associate publisher Chan Pui-man, and former editorial writers Fung Wai-kong and Yeung Ching-kee.

The six were charged with conspiracy to print, publish, sell, offer for sale, distribute, display or reproduce seditious publications between April 1, 2019, and June 24, 2021, under a colonial-era sedition law and soliciting sanctions from foreign forces on Beijing and Hong Kong between July 1, 2020, and June 24, 2021, under the National Security Law.

The sedition charges faced by all six were dropped in exchange for their guilty pleas.

The prosecution said the six directly participated in publishing, writing or creating purported news and opinion articles, that included seditious statements and appeals to the public to take part in anti-government protests.

The prosecution listed 161 relevant articles in the case to the court.

Facing the same charges as the six, Lai earlier pleaded not guilty and will have the case heard on Dec 1.

Lai also faces two additional collusion charges involving conspiring with others to seek foreign sanctions on China and the Hong Kong Special Administrative Region, between July 1, 2020, and Feb 15, 2021.

Three Apple Daily-linked companies were also charged with violating the National Security Law for Hong Kong by colluding with foreign forces to endanger national security and conspiracy to print, publish, sell, offer for sale, distribute, display or reproduce seditious publications.

Cheung's lawyer told the High Court that Cheung will appear in court as a prosecution witness in Lai's case.

The collusion charge is punishable by up to life imprisonment.

Three National Security Law-designated judges — Esther Toh Lye-ping, Susana Maria D'Almada Remedios, and Alex Lee Wantang — heard the guilty pleas of the six.

Hong Kong's Court of Final Appeal on Friday will hear an application for leave by the city's Department of Justice to overthrow a lower court's decision that allows British lawyer Tim Owen to represent Lai in his trial.