"We will not pay for your crisis," was the motto of the German campaign spearheaded by the anti-globalization network Attac.

Demonstrators said banks must be held to account for the crisis, rather than allowing employees and the world's poor to suffer as a result of the economic downturn.

A speaker for Attac said roughly 15,000 people had come to the Frankfurt demonstration. Several hundred police protected the entrances to office blocks in Germany's banking capital.

In Berlin, police estimated that several thousand people were taking part in the protest.

On pamphlets and placards, the demonstrators called for solidarity and an environmentally sustainable global economic system.

The protests came ahead of a meeting of the Group of 20 (G20) leading economies in London on April 2.

First of many rallies

The marches in Germany echoed events in London the same day, where tens of thousands of people gathered from around the world to stage a mass protest.

Braving cold and rainy weather the demonstrators were marching under the motto "Put People First" in a rally and carrying banners saying "Jobs, Justice and Climate."

More than 150 trade unions, peace activist groups and environmental protection organizations were behind the demo taking place in Hyde Park. Police estimated the crowd at up to 35,000.

Saturday's demo was the starting signal for what is to be a series of protests in the days leading up the April 1 and 2 summit.

Financial Fools Day

The police are most concerned about the potential for violence on Wednesday, dubbed "Financial Fools Day" by demonstrators, when an anti-war march will be held and climate change campaigners will set up a camp in the City of London financial district.

On that day, the protestors plan to hang suited effigies of bankers and march on the Bank of England headquarters shouting "Burn a Banker!"

The organizers stressed on Saturday that the protests were to be peaceful.

"If there are other groups who want to cause trouble, I don't want to see them anywhere near our event," said Brendan Barber of the British trade union confederation TUC.

World leaders, including US President Barack Obama on his first visit to Europe since he took office, will gather in London on Thursday for the G20 summit against a background of environmental crisis.

The NATO summit takes place Friday and Saturday in the French city of Strasbourg and across the border in Kehl, Germany.