JOS, Nigeria, Oct 31 (Reuters) - A Nigerian judge on Friday adjourned the trial of the country's most prominent militant leader to allow medics to check whether he is healthy enough to face treason and gun-running charges. The Movement for the Emancipation of the Niger Delta (MEND), whose campaign of sabotage against Nigeria's oil industry has cut output by around a fifth in recent years, has made the release of its leader Henry Okah one of its key demands. Okah still commands loyalty from well-armed factions in the creeks of the delta and his trial, behind closed doors in the central city of Jos, is being closely watched by his supporters. His lawyers and family say Okah, 43, needs medical care for a kidney ailment but the prosecution on Friday submitted what it said was a medical report showing he was fit to stand trial. The judge agreed to a request from Okah's lawyers that a second opinion be sought and adjourned the case to Nov. 21. Wilson Ajuwa, one of Okah's defence team, said his client needed tests which were not available in Nigeria. "We intend to go to the court of appeal to ask that he be allowed to go for tests abroad," Ajuwa told Reuters. Okah, who could face the death penalty if convicted, was arrested in Angola more than a year ago and extradited to Nigeria. His trial has been repeatedly delayed. Security sources have said parallel negotiations to reach a political deal which could see Okah released are also underway. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/ ) (Reporting by Shuaibu Mohammed; Writing by Nick Tattersall; Editing by Giles Elgood)