Some of the major Greek banks may have to close doors and merge with their rivals as part of the restructuring of the banking sector in midst of the country’s financial turmoil.

The country’s four big lenders – The National Bank of Greece, Eurobank, Piraeus and Alpha Bank – could be reduced to just two, Reuters reported citing a unnamed source.

However, the mergers would likely occur over the longer term, and would not typically impact customers as their accounts would be transferred to the bank’s new owner, the report said.

Greece defaulted on debt owed to the International Monetary Fund (IMF) last month, following which the ECB has frozen emergency funding for the country’s banks, causing their temporary closure as well as set a 60-euro daily limit on withdrawals from cash machines.

The country has recently rejected bailout terms offered by its international creditors which may compel ECB to maintain its cap, and lead the country’s banks to run out of cash soon.