LAGOS, July 23 (Xinhua) -- Nigerian President Umaru Yar'Adua on Tuesday in Abuja urged Nigerian athletes to the Beijing Olympic Games to shun prohibited substances that could tarnish the country's image.

Yar'Adua made the remarks while inaugurating the Doping Control Laboratory at the Abuja National Stadium, adding that athletes should use their natural talents and adhere to the core values in sports.

The president noted that the use of prohibited substances could bring dishonor to the country.

Yar'Adua praised the enormous sacrifice the athletes and their officials were making as they prepared for the 29th Olympiad, and also appreciated the efforts of Nigeria's past athletes.

The president said recently that his country should aim at collecting eight gold medals in Beijing.