Li Na of China serves to Tsvetana Pironkova of Bulgaria during their Paris Open tennis tournament at Coubertin stadium in Paris, Feb 7, 2012. [Photo/Agencies]

PARIS - French Open champion Li Na retired injured from her first-round match against Bulgarian Tsvetana Pironkova at the WTA Paris Indoor Open on Tuesday.

Third-seeded Li threw in the towel when she was 7-6 3-2 down as she was visibly suffering with a back problem and finally abandoned the match after receiving treatment courtside.

Li Na, the world number nine, has been struggling from a low competition form since her Paris Grand Slam victory last year, and the injury did no good to her preparation for a second French Open title and the upcoming Olympic Games.

Li Na of China retires from her match against Tsvetana Pironkova of Bulgaria during their Paris Open tennis tournament at Coubertin stadium in Paris, Feb 7, 2012. [Photo/Agencies]

Also on Tuesday, former world number one and the tournament's fourth seed Jelena Jankovic of Serbia pulled out with a thigh strain after failing to recover from a left thigh injury she picked up in a Fed Cup tie against Belgium last weekend.

"I am really disappointed not to play here," she told a news conference. "I don't know when I will be able to resume playing but I don't regret having played in the Fed Cup.