By Lefteris Papadimas

ATHENS Demand for a 20% stake in Greece's National Bank (NBG) held by the country's bank bailout fund was covered by more than six times on Tuesday, in the first day of a book-building process which ends later this week, a source with knowledge of the matter told Reuters.

"Demand covered 6.2 times the shares offered," the source involved in the process said on condition of anonymity.

After injecting about 50 billion euros ($54.37 billion) to prop up Greece's four largest lenders in return for shares during the country's decade-long debt crisis which ended in 2018, state-controlled bank bailout fund HFSF started divesting its stakes last month.

Eurobank was the first to end the state's participation in its share capital in October, weeks before S&P Global became the first among the “big three” rating agencies to upgrade Greece to investment-grade status, which it lost in 2010.

On Monday, HFSF concluded the sale of a 9% stake in Alpha Bank to UniCredit and announced plans to sell a 20% stake in NBG.

The shares in NBG, Greece's second-largest bank by market value, are being sold via a public offering and a private placement from Nov. 14-16 at between 5 and 5.44 euros per share.

The value of the 20% stake is estimated at about 1 billion euros ($1.09 billion).

HFSF currently holds a 40.4% stake in NBG and a 27% holding in Piraeus Bank,, Greece's third-largest lender. It has said it would aim to dispose of all its holdings in Greek banks before the end of 2025.

A source told Reuters on Monday that out of the 20% stake in NBG, 17% would be offered to funds and 3% to retail investors. If there was strong demand, HFSF would consider increasing the stake on offer to 22%.

JP Morgan, Goldman Sachs, Morgan Stanley and UBS have been appointed as global coordinators of the sale.

($1 = 0.9196 euros)

(Reporting by Lefteris Papadimas, Editing by Louise Heavens and Sharon Singleton)