The European Central Bank (ECB) again increased emergency liquidity funds for Greece's banks Monday, according to a Greek bank source who said the ECB may renew the hike "at any time" if necessary.

The new increase of the ECB's Emergency Liquidity Assistance (ELA) was the third since Wednesday and came as Greek savers continued withdrawing their money in large volumes from the country's banks.

Though the total amount of the new reserve was not divulged, the Greek source said ECB "governors may meet at any time ... including today or tomorrow" to review the situation, which is likely to evolve against an emergency eurozone summit in Brussels later Monday to seek an accord on Greece's debt crisis.  

On Wednesday the ELA ceiling was raised by 1.1 billion euros ($1.25 billion) to 84.1 billion euros, as the rate of Greek bank withdrawals rose. On Friday the reserve was increased a further 1.8 billion euros.

Greece's central bank said Greek business and private bank deposits had fallen by nearly 30 billion euros between December and April, to 128 billion euros.

Greek savers have been pulling their money from national banks at even higher rates in recent weeks, amid fears Athens may fail to reach agreement with its creditors to free up bailout funds needed to honour a June 30 debt repayment.