Bulgarian sprinter Tezdzhan Naimova has been banned for two years for manipulating a doping sample while middle-distance runners Vanya Netova and Raya Stoynova received two-year bans for doping.

Naimova was ruled to have tampered with her urine sample at an International Association of Athletics Federations (IAAF) out-of-competition test in Sofia on June 28.

"Her case is irrefutable and we had no choice but to ban her," Bulgarian athletics federation president Dobri Karamarinov told Reuters on Thursday.

The 21-year-old Naimova won the 100 and 200 metres at the world junior championships in Beijing in 2006.

Naimova, who had been widely regarded as one of the most promising young athletes, will miss the European indoor championships in Turin in March and the world championships in Berlin in August.

Netova and Stoynova were banned after testing positive for the anabolic steroid metanolon during competitions in Turkey and Greece.

Bulgarian athletics has been marred by a series of doping offences recently.

Middle-distance runners Daniela Yordanova, Vanya Stambolova and Teodora Kolarova, high jumper Venelina Veneva and hammer thrower Andrian Andreev have all tested positive in the last two years.