The Sueddeutsche Zeitung quoted an unidentified fund manager as saying that Cevian, which also owns stock in the Swedish group Volvo, had bought packets of Daimler shares.
Cevian declined to comment, the newspaper said.
On Monday, Daimler shares shot up on rumours that a hedge fund was interested in the company.
The shares have fallen by 42 percent in the past year, making Daimler’s stock attractive to investors.