Executive Editor-in-Chief Lam Man-chung was the eighth executive or journalist at the shuttered newspaper arrested in recent weeks as city authorities crack down on dissent and China's central government brings the semi-autonomous territory more under its control.

Lam was arrested on Wednesday, according to the South China Morning Post newspaper, which cited an unnamed source.

Associate Publisher and Deputy Chief Editor Chan Pui-man and editorial writers Fung Wai-kong and Yeung Ching-kee were also detained on Wednesday after their bail was revoked, local media reported.

All four were charged with conspiring to "collude with a foreign country or with external elements to endanger national security" under the city's year-old national security law.

Police confirmed four people, aged between 51 and 57, had been charged but did not identify them. They will appear in court on Thursday.

The Hong Kong Journalists Association criticised the "repeated targeting of journalists" from Apple Daily, stating that it was "shocked and puzzled".

In June, police raided the Apple Daily's offices, taking away hard drives and laptops as evidence.

The arrests of top executives, editors and journalists at the paper, as well as the freezing of millions of dollars worth of assets, led it to cease its operations last month.

It sold a million copies of its final edition.

Australian Associated Press