A block of 2% of Fairfax Media shares was bought in one transaction on Thursday, sparking speculation that mining magnate Gina Rinehart is increasing her hold in the company.
Some 42 million Fairfax shares were purchased at a price of A60 cents per share.
The ABC reports there has been intense speculation that Australia's richest woman would increase her stake in the company as she seeks seats on the Fairfax board.
Ms Rinehart recently confirmed she owns more than 13% of the company, which makes her the largest single investor.
If Thursday's purchase belongs to Ms Rinehart, it pushes her stake to 15%.