Why does my drum wobble like mad when its on a spin?

Recently, my washing machines drum has been wobbling eraticaly when its on a spin. When the wash is complete, the clothes are all clean, but when I wobble the drum myself it moves about in all directions. I've opened the top and the back of the washer but nothing seem's broken, or any evidence of breakege? Whats up with it and how can I mend it? Its a BEKO WMA 510