The spokesman for Niger's imprisoned opposition candidate says he has been transferred to a hospital in Niamey for medical attention after suffering health problems.

Hama Amadou's spokesman said Friday that Amadou would return to prison after the hospital visit. Malam Mamane Sani did not specify the health condition.

Sani also confirmed that Amadou would participate in the presidential runoff vote scheduled for March 20, despite an announcement by the opposition Tuesday that he would not participate because of vote rigging.

President Mahamadou Issoufou won 48 percent of the Feb. 21 vote, short of the majority he needed to avoid a second round.

Amadou, a former prime minister, has been detained since November for his alleged involvement in a baby-trafficking scheme, a charge he has dismissed as politically motivated.