An image of Bruni wearing only a pair of black leather boots was published in the February edition of DT.
Bruni was also pictured wearing a wedding band, which is set to fuel the rumor that she and the French leader have wed in secret.
A spokesman for the magazine said the photograph was taken before her relationship with Nicolas Sarkozy was officially confirmed.
The Italian-born Bruni, 40, said in a recent interview that she "was not married yet," although she and Sarkozy had plans to make their relationship official.
Sarkozy, 52, and Bruni have been on the front pages of newspapers and magazines since his divorce from his second wife Cecilia in October. In December, Bruni accompanied the president on his trip to Egypt and later to Jordan.
The president's own popularity ratings have plunged lately, with voters anxious over economic problems.
Another photo, where Bruni is shown topless, has been posted on various Internet blogs. The origin of the photo is unclear, but it could be from the same set of photos as those published in the Spanish magazine.
Since getting together with Sarkozy, the supermodel has had photos taken for an advertizing campaign by the Italian carmaker, Lancia. Bruni posed barefooted in a light evening garment holding a guitar.
