Police closed off main roads in the centre of Frankfurt and set up check points on highways around the city as part of a heavy security operation to protect Germany's financial capital.

The protesters are angry at the misery they say governments are inflicting on people with their response to the crisis, which has intensified since inconclusive elections in Greece this month fueled concerns about its future in the euro zone.

"We're protesting against the Europe-wide policy of impoverishment by the troika," said a spokeswoman for the 'Blockupy' anti-capitalist movement, who put the number of protesters at 25,000. Police said there were 20,000.

The troika refers to European Central Bank, International Monetary Fund, and European Union officials who are supervising bailout programmes extended to Greece, Portugal and Ireland.

The Frankfurt-based European Central Bank ECB.L is at the centre of the policy response to the crisis and has faced calls from politicians, investors and protesters to do more.

The central bank says it has already headed off a major credit crunch with unprecedented funding operations in December and February that unleashed over 1 trillion euros into the financial system.

Saturday's march - the final demonstration in a four-day-long 'Blockupy' protest - passed off peacefully and without police detaining any demonstrators.

The protest followed a legal scrap between activists and authorities over whether the demonstrations should be allowed to proceed.

A court on Monday gave the go-ahead for a rave dance party organised by protesters on Wednesday and Saturday's protest, but ruled against demonstrations taking place on other days. Several hundred activists were detained earlier in the week for defying that ban.

(Reporting by Till Weber, Ludwig Burger and Paul Carrel; Editing by Sophie Hares) `

• A Permanent Economic Emergency