FRANKFURT (Reuters) - German police began peacefully removing anti-capitalist protesters from outside the European Central Bank's headquarters on Wednesday at the start of a planned four-day long 'Blockupy' demonstration.

The police moved in after some 200 protesters angry at the way the financial crisis is affecting many people defied a request to leave their camp outside the 36-storey, glass-fronted skyscraper in Germany's financial capital.

The ECB building has already been the target of protesters once this year, having its windows smashed and paint bombs hurled at it during ugly riots at the end of March that left one police officer in intensive care.

The bank is worried about staff safety and police have erected fences around its headquarters in the heart of Frankfurt's banking district.

To avoid the start of the protest on Wednesday, the ECB's 23-member group of policymakers brought forward its mid-month meeting, which they normally reserve for non-monetary policy issues, by one day to Tuesday.

Frankfurt police have drafted in reinforcements from other German states to cope with the protests. Some 5,000 police are ready to be deployed.

There has been a legal scrap between the protesters and authorities over whether the demonstrations should be allowed to go ahead. A court on Monday gave the go-ahead for a rave on Wednesday and protests on Saturday but ruled against them taking place on the other days.

The ECB has also shifted a farewell event for outgoing board member Jose Manuel Gonzalez-Paramo, due to be attended by policymakers from around the world.

The gathering was originally to be held at one of Frankfurt's plushest hotels, just a stone's throw from the ECB's headquarters. Instead, it will now be held out of town with guests to be told the exact location only hours beforehand.

Commercial banks who have offices in the protest zone are also expected to ship staff to other locations to avoid problems.

(Reporting by Tilman Blasshofer and Sakari Suoninen, writing by Paul Carrel, editing by Gareth Jones)