LONDON (Reuters) - Tennis will introduce biological passports for players and increase the number of blood tests done each year, the sport's anti-doping agency said on Thursday.

A number of players, including 17-times grand slam winner Roger Federer, had called for the sport to up its anti-doping measures in the wake of high-profile cases in other sports.

A biological passport is an electronic document containing test results collated over time that can be used to detect changes that might indicate doping.

"The implementation of the athlete biological passport is an important step in the evolution of the Tennis Anti-Doping Program as it provides us with a great tool in the fight against doping in our sport," said International Tennis Federation (ITF) president Francesco Ricci Bitti in a statement.

According to figures on the ITF website (www.itftennis.com), the governing body carried out only 21 out-of-competition blood tests in the professional game in 2011.

Cycling's governing body, the UCI, carried out more than 3,314 out-of-competition blood tests in the same year.

The UCI introduced biological passports in 2008 to track any blood changes in riders against an original profile.

(Reporting by Toby Davis,; editing by Tony Jimenez)