Berlin  - German investor confidence posted its second unexpected rise in two months Tuesday, analysts attributing this to lower energy prices and a stronger dollar providing a boost to exports from the eurozone.

Drawn up by the Mannheim-based Centre for European Economic Research, the ZEW September index rose to minus 41.1 from minus 55.5 points in August.

The ZEW appended a special note on the fall-out from the collapse of US bank Lehman Brothers, saying that a separate analysis of 31 answers that came in after the bankruptcy showed that the economic expectations for Germany had not deteriorated.

The ZEW said there were two essential reasons for the recovery of expectations: "On the one hand, the ongoing decline of the oil price eases the burden on consumers and firms. On the other hand, the tendency of the euro in the past weeks to depreciate against the US dollar benefits German exporters."

ZEW President Wolfgang Franz added: "Due to the declining oil price the inflationary pressure is decreasing. This should improve the perspectives for German consumption." (dpa)