Ugandan former presidential candidate Kizza Besigye has gone on hunger strike, his lawyer told AFP Wednesday, months into his detention by authorities after he was snatched from neighbouring Kenya.

Besigye was once President Yoweri Museveni's trusted personal doctor but has become a government target since joining the opposition 25 years ago and unsuccessfully running for president four times.

He was abducted in November and has been facing the death penalty on treason charges in a court martial that his wife, UNAIDS executive director Winnie Byanyima, has called a "sham".

Following media reports of the move, lawyer Elias Lukwago told AFP that Besigye, 68, began his protest on Monday, because he "feels he has been left with no choice but to go on hunger strike".