Shares in Greek banks have fallen up to 30% after plans to merge two of them were called off.
National Bank of Greece and Eurobank fell by 30% in morning trade on Monday, while Alpha and Piraeus lost up to 20%.
On Sunday, the finance ministry said thr merger would not go ahead, although the four would be recapitalised.
The BBC reports there had been fears a merged bank would be too dominant in the market.
Recapitalising the banks is a condition of Greece receiving support from the European Union and the International Monetary Fund.
In a statement, the central bank said:
"The Bank of Greece confirms that the recapitalisation process for the four systemic banks [National Bank, Alpha, Eurobank and Piraeus] is proceeding normally and will conclude in April in any case."