Thousands march in Frankfurt against austerity measures FRANKFURT (Reuters) - At least 20,000 demonstrators marched through Frankfurt on Saturday in a peaceful protest against austerity measures implemented to tackle the intensifying euro zone debt crisis. 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. "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 programs extended to Greece, Portugal and Ireland. The Frankfurt-based European Central Bank (ECB) is at the centre of the policy response to the crisis and has faced calls from politicians, investors and protesters to do more. 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 organized 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