A Nigerian court on Wednesday refused to release a Shiite Muslim cleric who has been in custody since 2015 following deadly clashes between troops and his supporters, his lawyer said.Ibrahim Zakzaky, who leads the Islamic Movement of Nigeria (IMN), and his wife, Zeenat, are standing trial on charges of culpable homicide and unlawful assembly.At the state high court in the northern city of Kaduna, soldiers were on guard, barring access to both the media and the public in a move denounced by his lawyer Maxwell Kyon."We find that to be quite troubling because the definition of free trial should include access to the courtroom by the public," Kyon told AFP after the hearing. "My client was in court today. The court refused to grant him bail."His legal team had called for his release on health grounds, saying he needed urgent medical care abroad but the court denied the request. "The court is of the view that we were not able to establish that he is sick, and that even if he is sick the (intelligence services) can provide the medical attention he needs," he said. The judge acknowledged the defendant had been kept in custody for nearly three years but pledged a "speedy trial" would take place, Kyon added.Zakzaky was remanded in custody until a further hearing on January 22.The pro-Iranian cleric's court appearance comes after fresh unrest involving the IMN last week, which human rights groups said left at least 45 people dead.Soldiers and police allegedly opened fire on demonstrators calling for Zakzaky's release in Abuja. The army put the death toll at six with 400 IMN supporters arrested.Zakzaky, who is in his mid-sixties, has been at loggerheads for decades with Nigeria's secular authorities because of his call for an Iranian-style Islamic revolution.He lost the sight in one eye during the 2015 clashes in the northern city of Zaria, during which soldiers killed more than 300 IMN supporters and buried them in mass graves.Northern Nigeria is mainly Sunni Muslim with Shia in the minority.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.