Hong Kong authorities have strengthened a crackdown on 16 overseas-based activists who were previously targeted by bounties on suspicion of endangering national security.

Hong Kong has tightened prison rules, allowing authorities to restrict visits on national security grounds.

It’s been years since Hong Kong’s mass arrests of activists devastated its pro-democracy activism.

Hong Kong police on Tuesday arrested six people, including a former organizer of the city’s decades-long annual vigil that commemorated China’s Tiananmen Square crackdown, for allegedly publishing seditious social media posts.

China has promoted Hong Kong's top security official to the territory's No. 2 spot as Beijing clamps down on free speech and political opponents.