Erste Group Bank has bought a 49% stake in Santander's Polish bank for around 6.8 billion euros ($7.7 billion), turning Austria's largest lender into one of the most important banks in Poland and freeing up billions for Santander .

Banco Santander agreed to sell most of its Polish assets to Austria’s Erste Group Bank, continuing a wave of dealmaking among European lenders.

Erste Group Bank AG is exploring buying a major stake in Banco Santander SA’s Polish unit, seizing an opportunity to expand in one of Europe’s fastest-growing markets, according to people familiar with the matter.