"I am determined to lead the transition," he said in a speech.
"So that one day we will be able to decide the fate of our country through a democratic, transparent process right up to the ballot box."
The demonstration in the Theresienwiese area was held at the same time as world leaders gathered for a security conference nearby. The aim was to condemn the Iranian regime and its deadly violence against the population.
Similar protests against the Iranian government are also planned to be held in Toronto, Canada, and Los Angeles, USA, on Saturday.
