Germany's biggest bank, Deutsche Bank
The bank tapped the ECB's long-term refinancing operation -- aimed at propping up Europe's banking system -- as a means of pumping cash into their operations in Italy and Spain, said the source, who has direct knowledge of the matter.
Deutsche Bank declined to comment.
In early February, chief executive Ackermann said Deutsche had not taken part in an earlier ECB tender but signalled the lender could take advantage of future offers for cheap cash if it was economically sensible to do so.
Germany's second biggest lender Commerzbank
The move marks a more pragmatic approach toward receiving cheap cash from the European Central Bank, mirroring a change of attitude by rival Barclays
Tapping the central bank for loans is currently cheaper than refinancing on commercial markets, and helps to avoid a mismatch between loans and deposits at operations in countries hit by an economic slowdown.
A total of 800 banks borrowed money in the ECB's latest liquidity operation, fuelling expectations that credit will flow to businesses and borrowing costs will ease for governments hit by the euro zone crisis.
In the first long-term refinancing operation Commerzbank's mortgage unit Eurohypo
European Central Bank president Mario Draghi said 460 German banks participated in the most recent LTRO. Around 42 billion euros was taken to fund operations in Germany, according to Reuters calculations.
Germany has 2,000 banks, while Britain has just 405, Spain 415, Italy 785, Ireland 590 and France 1,147, according to ECB statistics.
The Financial Times newspaper also reported on Friday that Deutsche Bank had taken advantage of the ECB's LTRO scheme.
(Editing by Sophie Walker)