WASHINGTON/NEW YORK, April 11 (RIA Novosti) - Christie's International sold a nude photo of France's first lady Carla Bruni-Sarkozy for $91,000, over 20 times its pre-auction estimate, the auction house said on Friday.

The photo, taken in 1993 by Michel Comte, was initially expected to fetch $3,000-$4,000. It was bought by Alex Cao, a dealer bidding on behalf of an unknown Chinese collector.

Prices for photos of the former model turned singer have significantly increased since French President Nicolas Sarkozy, 53, and Bruni, 40, tied the knot at a private ceremony at the Elysee Palace on February 2, 2008, less than four months after divorcing his second wife Cecilia.

Last February, a Bruni photograph taken by Karl Lagerfeld in 1998 fetched $5,760, while a 1994 Compte print sold for a mere $960.

Since Sarkozy's divorce in October 2007 the couple have constantly been on the front pages of newspapers and magazines. Naked photos of Carla Bruni-Sarkozy appeared in U.K. tabloids during the French couples' official visit to Britain last month.

The photograph together with 135 works, part of a collection owned by German collector Gert Elfering, fetched a total of $4.2 million on Thursday surpassing estimates by more than $1 million.

Elfering's collection also included models Lauren Hutton, Kate Moss, Gisele Bundchen and a photo of the former actress Brigitte Bardot taken by American photographer Richard Avedon sold for $181,000.

The auction's top lot, however, was Helmut Newton's "Sie Kommen (Naked and Dressed)" which fetched $241,000.