Fortis healthcare along with its founders have made an open offer for all of

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Parkway Holdings for S$3.21 billion (US$2.3 billion), an adviser to the hospital chain said.

RSC Healthcare, 51 percent owned by billionaire Singh brothers and the remainder by Fortis, has made the open offer at S$3.80 a share and has tied up all funds, Sachindra Nath, CEO of Religare, advisor to Fortis Healthcare, told Reuters.

Fortis, which owns roughly 25 per cent of Parkway, was keen to build a controlling stake in the company before Khazanah made a surprise $835 million offer last month to lift its stake from 23.5 per cent to 51.5 per cent.

Parkway operates 16 hospitals across Asia including Singapore, Malaysia, India and China. Its prized assets are Singapore hospitals, Gleneagles and Mount Elizabeth, whose patients include many wealthy businessmen and politicians.

With a combined fortune estimated at $3 billion by Forbes magazine -- good for 17th place on its India rich list -- the Singh brothers have the means and access to capital to take on the Malaysian fund.