A Nigerian man facing imminent execution in Indonesia tearfully told a court that police electrocuted his genitals to force him to confess to possessing heroin.

Michael Titus Igweh is among several prisoners on death row whom lawyers and human rights groups are frantically lobbying to save from the firing squad amid claims they were tortured and their legal cases riddled with corruption, errors and miscarriages of justice.

Michael Titus Igweh, who is facing execution in Indonesia within days, tells a court that police electrocuted his genitals to extract a confession. Credit:Andri Donnal Putera

"I was constantly beaten, and my genitals electrocuted until I was helpless," the clothes importer, who was sentenced to death in 2003 for possessing 5.8 kilograms of heroin, told the Tangerang District Court in May. "In fact, I was threatened to be shot."

Sources have told Fairfax Media the third wave of executions in Indonesia could be held within days. It is understood the Nigerian and Pakistani embassies have now been notified that their nationals are among those to be killed.