As Germany's top parties were set to hold final rallies ahead of Sunday's vote, the Fridays for Future youth marches made the case that the political class has let down the younger generation.

"The political parties haven't taken the climate catastrophe seriously enough," Luisa Neubauer, who runs the group's German chapter, told AFP.

She said Germany, as one of the world's top emitters of greenhouse gases, had an outsize responsibility to set an example, with time running out to reverse destructive trends.

"That is why we are calling this the election of a century," she said.

The race has boiled down to a two-way contest between Social Democrat Olaf Scholz, the centrist finance minister, and Armin Laschet from Merkel's conservative Christian Democrats. Both were set to address crowds later Friday, in Cologne and Munich respectively.

Polls give Scholz a small lead of about 26 percent over Laschet at around 22 percent, with the candidate from the ecologist Greens, Annalena Baerbock, trailing in the mid-teens.

Despite the urgency of the climate issue for a majority of Germans, particularly in the aftermath of deadly floods in western Germany in July, this has failed to translate into strong support for the relatively inexperienced Baerbock.

Baerbock, who joined one of the Fridays for Future rallies in Cologne, told Die Welt newspaper that she hoped the protests would give her party "tailwinds" heading into the vote. "The next government has to be a climate government -- that will only work with a strong Green party."

- 'Unfair burden' -

More than 400 "climate strikes" were taking place across Germany, with the Swedish Thunberg, who inspired the two-year-old movement, due to speak outside the Reichstag parliament building in Berlin.

Thousands gathered on the lawn there from late morning bearing signs reading "Climate now, homework later", "It's our future" and simply "Vote".

"Climate is an important issue and if this continues things are going to get worse and worse," 14-year-old pupil Louise Herr told AFP.

The German protests are part of a global climate strike in more than 1,000 communities around the world, Fridays for Future said.

Their central demand is to limit the warming of the Earth to a maximum of 1.5 degrees Celsius (2.7 Fahrenheit) as laid out in the 2015 Paris climate accord.

Despite Merkel's vocal support of climate protection measures, Germany has repeatedly failed to meet its emission reduction targets under the pact.

In a landmark ruling in April, Germany's constitutional court found the government's plans to curb CO2 emissions "insufficient" and placed an "unfair burden" on future generations.

- Greens as junior partner? -

In September 2019, the Fridays for Future climate movement drew huge crowds in cities and towns around the world including 1.4 million protesters in Germany, according to organisers.

"The climate crisis cannot be solved through party politics alone," Thunberg told reporters ahead of her appearance in Berlin.

"We can't just vote for change, we also have to be active democratic citizens and go out on the streets and demand action."

Around 60.4 million Germans are called to the polls on Sunday and most voters cite climate protection among their top priorities.

All three leading parties have said they aim to implement a climate protection agenda if elected, with the Greens presenting the most ambitious package of measures.

However, the Fridays for Future activists have said even the Greens' official programme falls short of what is needed to stick to the 1.5 degree Celsius temperature rise.

The Greens want to end coal energy use by 2030 instead of the planned 2038 and end the production of combustion engine cars the same year.

While the party is expected to fall far short of its ambition to win Sunday's election and place Baerbock in the chancellery, polls indicate it has a good chance of joining a ruling coalition as a junior partner under Scholz or Laschet.

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