The source said that Auna shareholders received an offer for the entire business from Kohlberg Kravis Roberts, and partners Goldman Sachs and BC Partners.

Auna’s leading shareholders include the Spanish power groups Endesa SA and Union Fenosa SA, as well as bank Banco Santander Central Hispano SA. Initially, they had been aiming for the auction to raise as much as $13bn euros ($14.33bn), but then lowered the asking price to 11bn euros ($13.13bn). According to the report, Merrill Lynch, which is acting for the shareholders, had received an offer above the asking price, and another below it.

It is thought the sale has been triggered by the desire of Endesa and Union Fenosa to raise cash to cut debt, and in the case of Endesa, to distribute a bonus dividend.

The more likely buyers are thought to be private equity companies. According to recent press reports, BC Partners has teamed up with US risk capital group Kohlberg Kravis Roberts Co and Goldman Sachs Capital Partners to bid up to 12.5bn euros ($14.92bn) for Auna.

A rival bid is also thought to be on the cards from a consortium of Carlyle Group LP, Providence Equity Partners, Permira, and Blackstone Group, which according to various reports have already made separate bids for Auna’s fixed-line assets, including the cable network, and the wireless business Amena Movil. Auna is Spain’s third largest mobile operator.