German business sentiment dropped for the fourth successive month in August to reach its lowest level since March 2010, in a sign that domestic firms are increasingly vulnerable to the ravages of the euro zone crisis.

The Munich-based Ifo think tank said on Monday its business climate index, based on a monthly survey of some 7,000 firms, fell to 102.3 in August from a downwardly revised 103.2 in July.

A Reuters poll of 40 economists had forecast a fall to 102.6 from an originally reported 103.3.