Lam Cheuk-ting, Ted Hui and at least 14 others have been detained over protests last year, triggered by the government's decision to pass an extradition bill allowing suspects to be sent to mainland China to stand trial.
Local media said six activists were wanted on suspicion of secession or colluding with foreign forces, crimes that the new law punishes with up to life in prison.
"Its sheer size justifies the scrutiny," said Dania Rajendra of the activist group Athena, a coalition which is focused specifically on Amazon's corporate activity and treatment of workers.
Organisers of the march called for the German government to implement the 2015 Paris plan to shift the world economy from fossil fuels.
Subscribe to our Youtube channel for all latest in-depth, on the ground reporting from around the world.
Copyright © 2021 TRT World.