German business sentiment dropped for the sixth successive month in October, in a surprise fall that was bigger than even the lowest forecasts, signaling that the euro zone debt crisis is hitting home in Europe's largest economy.

The Munich-based Ifo think tank said on Wednesday its business climate index, based on a monthly survey of some 7,000 firms, fell to 100.0 in October from 101.4 in September.

A Reuters poll of 45 economists had forecast a slight rise to 101.5, with figures ranging 100.4 to 102.5.

(Reporting by Berlin Bureau)