The European Central Bank on Wednesday raised the maximum emergency funding that Greek banks can obtain by 1.4 billion euros ($1.5 billion), a banking source said.

The increase -- which brought the overall ceiling on Emergency Liquidity Assistance (ELA) to 76.9 billion euros -- came as Athens sought to conclude marathon talks with its EU-IMF creditors on a new loan deal.

Taking into account other unused amounts, Greek banks have a total of 3.0 billion euros in funding available to them this week, the banking source added.

In March, they lost 2.0 billion euros to withdrawals from private and business account holders, the Bank of Greece said in a statement Wednesday.

Greek banks are dependent on the ECB for financing, but the eurozone's central bank no longer accepts Greek sovereign bonds as collateral for loans.

It had done so previously under a special waiver mechanism, but rescinded that waiver until Athens' new anti-austerity government under Prime Minister Alexis Tsipras agrees a new debt deal with its creditors.

Without the waiver, Greek banks now rely solely on ELA, which is more expensive than normal central bank refinancing operations.

Tsipras's government has said it is hoping to conclude by early May a deal with its international creditors that would give access to some 7.2 billion euros still left in the country's EU-IMF bailout package.