BONN, Germany — Thousands of demonstrators have marched through Bonn to protest the use of fossil fuels ahead of a global climate conference being held in the western German city next week.

Participants in Saturday’s event carried banners with slogans that included “Revolution Not Pollution,” ”Frack Off Our Land” and “Trump: Climate Genocide.”

Protest organizers say some 25,000 people took part in the demonstration. Police had no official estimates, but said the size of the crowd was “clearly more” than the 10,000 expected.

Many protesters criticized the German government’s reliance on coal-fired power plants for much of the country’s energy even as it pursues ambitious targets for renewable sources.

Protester Holger Heinrich said: “Germany finally has to contribute, and not only talk.”

The 2017 United Nations Climate Conference known as COP23 begins on Monday.