Some 3,000 people demonstrated in the western German town of Hanau on Saturday against hate and contempt for the human race, according to the police numbers.
They carried posters with inscriptions such as "Must people be killed first for you to be outraged?" or "Human rights instead of rightists."
The organizers had expected 2,000 participants for the demonstration from Freiheitsplatz - which translates as Freedom Square - in the city centre to the two places where a 43-year-old German shot dead nine people with foreign roots on Wednesday evening.
The marksman also killed his 72-year-old mother before turning his gun on himself.
It has since been revealed that the perpetrator had a deeply racist mindset and was mentally ill.
The Green politician Cem Özdemir laid a wreath for the victims of the attack in Hanau on Saturday.
It was difficult to find words, he said in the Heumarkt (Haymarket), where the killer shot some of his victims.
Özdemir said he hopes "that this year will go down in history as the year in which the [German] republic gets serious about tackling right-wing radicalism."