Greek depositors withdrew €700 million ($898 million) from the country's banks on Monday, fueling fears of a bank run amid the growing political disarray.

With deposits falling, Greek banks become even more dependent on the European Central Bank to meet their funding needs, exposing the central bank to potentially huge losses if Greece leaves the euro area.

Greek President Karolos Papoulias told the country's political leaders that bank withdrawals plus buy orders received by Greek banks for German bunds totaled some €800 million on Monday, a transcript of his comments said. A central bank official confirmed the figures.

"The strength of banks is very weak right now," Mr. Papoulias said, citing a conversation he had with Greek central-bank Gov. George Provopoulos.

Monday's deposit withdrawal far outpaced Greek banks' steady decline in deposits since the start of the country's debt crisis in 2009, as depositors withdraw cash and transfer funds overseas. In the past two years, deposit outflows have generally averaged between €2 billion and €3 billion a month, though in January they topped €5 billion.