Nigeria has banned eight athletes for doping, four of them gold-medal winners and one a silver medallist at the All Africa Games last year.
Long jumpers Chinazom Amadi and Samson Idiata, weightlifter Elisabeth Onua and wrestler Patience Opuene were all barred following failed drug tests at the games in Brazzaville, Republic of Congo, in September, where they won gold.
Wrestling silver medallist Ebi James Igbadiwei was also suspended.
The three other athletes, sprinter Deborah Odeyemi and para-athletes Sunday Ezeh and Thomas Kure, failed tests in Nigeria. Odeyemi ran on Nigeria's women's 4 x 100-meter relay team at the 2015 world championships.
Seven of the athletes were given four-year bans. Weightlifter Onua, who tested positive for the diuretic Amiloride, received an eight-year ban after multiple violations.
Nigeria's National Anti-Doping Committee said the athletes' All Africa Games medals and winnings would be sent back to organizers.
The Nigerian cases follow a severely troubled doping control program at the All Africa Games, which was described as "chaotic" and "ineffective from the start" by World Anti-Doping Agency independent observers in Republic of Congo.
National and international sports federations weren't informed of the failed doping tests for months after the games, which is Africa's premier multi-sport event.