The German central bank or Bundesbank supplied its counterpart in Cyprus with banknotes as the island's banks reopened Thursday after an unprecedented 12-day lockdown, financial sources said.
"The operation was led by the Bundesbank and the transportation of the notes was coordinated by the European Central Bank," one of the sources told AFP.
Another source said that only one national central bank was involved in the operation.
According to the business daily Handelsblatt, five billion euros ($6.4 billion) worth of banknotes were flown to Cyprus in a Lufthansa jet.
Other media reports put the amount at between 1.5-5.0 billion euros.
Neither the Bundesbank nor the ECB were willing to confirm the numbers, but did not deny them either.
Euro banknotes are not printed and stocked by the ECB in Frankfurt, but by the different national central banks which make up the eurosystem. But a number of central banks are supplied by others, as is the case for Cyprus.
Cypriots stayed calm as banks reopened on Thursday after a nearly two week lockdown, with tight capital controls stopping customers from draining the island's coffers after its eurozone bailout.