German investors confidence over the economic outlook fell for the fourth straight month in April, due to concerns on crisis in Ukraine, a survey showed on Tuesday.

The Center for European Economic Research (ZEW) based in Mannheim said its index for investor expectation for Europe's largest economy in the next six months declined by 3.4 points to 43.2 points.

"The cautious expectations in this month's survey are likely to be caused by the Ukraine conflict, which still creates uncertainty," ZEW said in a statement.

The European Union accused Russia of stirring conflicts in Ukraine and introduced punitive measures including bank account freezes and travel bans on Russian officials. It also threatened further economic sanctions on Russia, which is Germany's third biggest trading partner outside Europe and delivers 31 percent of the crude oil and natural gas imported by Germany.

Earlier this month, four leading economic institutes in Germany warned that the tense situation in Ukraine was a uncertain factor for the outlook of German economy.

ZEW said on Tuesday that its survey based on 238 interviews of analysts found that experts' assessment of the current economic situation for Germany improved in April. The correspondent index gained by 8.2 points to 59.5 points.

This might also explain to some extent the drop in investors' expectation for the German economy in the next half of the year, said the institute.

"In their view, the German economy is already growing at a considerable pace," the report said.