Tens of thousands of Germans took to the streets Saturday to protest against nuclear power, increasing the pressure on Chancellor Angela Merkel on the eve of a critical state election.

Under the banner "Fukushima means: no more nuclear power stations," marches took place in Hamburg, Cologne, Munich and capital Berlin, ahead of the vote in wealthy Baden-Wuerttemberg Sunday, where the nuclear issue is set to play a key role.

In Berlin alone, police said the "organisers' aim of getting 50,000 would be basically achieved."

"Today's demonstrations are just the prelude to a new, strong, anti-nuclear movement. We're not going to let up until the plants are finally mothballed," said a spokesman for one of the main organisations running the protests.

"We call on the government to stop representing the interests of the energy companies and listen to the people, who are no longer prepared to accept the risks of atomic energy," added Jochen Stay, spokesman for Ausgestrahlt.

Merkel decided on March 14, in light of the nuclear crisis in Japan, to hold a three-month moratorium on extending the lifetimes of Germany's 17 reactors and to shut off the oldest seven temporarily pending safety checks.

Despite her protests to the contrary, electors believed this move to be electioneering, and reported comments from the economy minister seemingly confirming this added to Merkel's woes ahead of Sunday's must-win election.

Her conservative CDU party was bracing for a tight result in Sunday's vote in a state they have held for 58 years.

Polls show that the ecologist Greens, spurred by anti-nuclear sentiment in the country, could make history and garner enough votes with the opposition Social Democrats (SPD) to govern with Germany's first ever Green state premier.

"We have to learn from Japan: nothing is impossible," read one placard in Berlin as a float manufactured by the Greens portrayed a nuclear reactor being consigned "to the dustbin of history."