"PPF believes the digital transformation of ProSieben will create value for all shareholders," privately-owned PPF said in a statement. "PPF is looking forward to liaising with the management and supervisory board of ProSieben in this digitalization process."

Frankfurt-listed ProSiebenSat.1 shares were up 1.65%.

PPF, founded by the now deceased Petr Kellner, has investments across 25 countries in banking, telecoms, manufacturing, real estate, biotech and other industries.

The group, which also owns the CME group that operates dozens of channels in six central and east European markets, is now controlled by Kellner's widow, Renata Kellnerova.

"We are pleased that Ms Kellnerova sees ProSiebenSat.1 as an attractive investment and has placed her trust in our company," a spokesperson for ProSieben said, adding there had been initial contact with PPF, which was very positive.

MFE-MediaforEurope, which is controlled by the family of former Italian Prime Minister Silvio Berlusconi and has built a potential stake of up 29.9% in ProSieben, earlier this month ruled out a full merger and takeover bid at present but said closer cooperation was possible.

(Reporting by Jan Lopatka, Klaus Lauer and Christoph Steitz; Editing by Mark Potter)