It comes as the Greek government and its international creditors blamed each other for failing to reach a deal over economic reforms.
That failure is holding up the release of €7.2bn (£5.2bn) in bailout funds.
About €30bn was withdrawn from Greek bank deposits between October and April, the central bank added.
The central bank also warned the country's economic slowdown would accelerate without a deal.
"Failure to reach an agreement would... mark the beginning of a painful course that would lead initially to a Greek default and ultimately to the country's exit from the euro area and, most likely, from the European Union," the Bank of Greece said in a report.
"Striking an agreement with our partners is a historical imperative that we cannot afford to ignore." » | Wednesday, June 17, 2015
