The reported merger of Greek banking groups EFG Eurobank and Alpha Bank would create Bulgaria's third largest lender, overtaking National Bank of Greece-owned United Bulgarian Bank (UBB).

According to reports by Financial Times and Reuters, the two Greek groups were set to announce on August 29 a merger deal including equity swaps and a 500 million euro capital boost from Qatar.

The merger would dispel fears that Alpha Bank or Eurobank would require assistance from Greece’s 10 billion euro bank stability facility to shore their capital ratios, which would lead to nationalisation, Financial Times said.

One unnamed executive was quoted by FT as saying that the merger between Greece's second and third-largest banking groups was a "done deal". According to Reuters, Alpha Bank president Yannis Costopoulos would be the president of the new bank, while the chief executives of the two banks, Nicholas Nanopoulos from Eurobank and Dimitris Mantzounis from Alpha Bank, would be chief executives of the new lender.

If regulators approve it, the new group would be euro zone's 25th largest lender. The new entity would have assets estimated at 150 billion euro and 80 billion euro in deposits.

In Bulgaria, EFG Eurobank owns Postbank, with assets of 5.85 billion leva, while the Alpha Bank branch in Sofia has assets of 2.08 billion leva. UBB is currently the third largest bank in the country, with assets of 7.01 billion leva.

But it could be a short-lived fall for UBB if speculation cited by FT proves correct and NBG makes a merger offer for Piraeus Bank, also present in Bulgaria.