Crowds gathered outside a Hong Kong court early on Saturday, chanting "release all political prisoners".
Inside was the first hearing for two executives of pro-democracy newspaper Apple Daily charged under the city's sweeping national security law.
Some were holding yellow umbrellas, a symbol from the 'Umbrella Movement' in 2014 that called for democracy and universal suffrage.
Editor-in-chief Ryan Law, and CEO Cheung Kim-hung, were among five Apple Daily executives arrested on Thursday when 500 police raided the outlet's newsroom.
They are charged with collusion with a foreign power to endanger national security, and were denied bail. The other three were released on bail late Friday night.
Police said dozens of the newspaper's articles were suspected of violating the contentious national security law. It was the first time media articles have been cited as potentially falling foul of the legislation.
The case has drawn international criticism and raised alarm over press freedom.