Official figures show that euro zone banks deposited the biggest amount of overnight funds at the ECB for more than a year on Monday. The data are seen as a signal of banks' wariness of lending to each other.
Banks put €346.36 billion on deposit for 24 hours at the European Central Bank, the highest amount since June 2010.
The level of deposits at the ECB bank is an indicator of the reluctance of banks to lend to each other on the pivotal inter-bank market.
The money deposited earns an interest rate of 0.25%, which is less than the rate available on the inter-bank market.
Banks become reluctant to lend to each other notably when they are concerned about the capacity of the borrower to repay the loan.
