HONG KONG, Nov 22 (Reuters) - 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."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.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."