The leader of Nigeria’s minority Shi’ite Muslims was denied bail on Wednesday, days after the group revealed that more than 40 of its members were killed by security forces shooting at protesters calling for his release.

During a regular hearing at the Kaduna High Court,Justice Gideon Kurada said that no substantial medical evidence had been produced to grant Zakzaky bail.

According to the judge, the accused should remain in custody throughout the period of his trial. The next hearing was set for Jan. 22 2019.

Ibrahim Zakzaky, leader of the Islamic Movement of Nigeria (IMN), has been held in detention since December 2015 when the army killed hundreds of his followers at his compound and a nearby mosque and burial ground in northern Kaduna state.

He is facing trial for murder, culpable homicide, unlawful assembly, disruption of public peace and other charges following the 2015 violence. He was charged in April.

The treatment of IMN and Zakzaky’s detention for nearly three years has drawn criticism from human rights groups and raised fears that the group may become radicalised – just as the Sunni Muslim militant group Boko Haram turned into a violent insurgency in 2009 after police killed its leader.

On three separate days this month, security forces opened fire with live ammunition on IMN members in the capital, Abuja, when they marched in their hundreds to demand his release, leaving at least 45 protesters dead, the group said.

Around half of Nigeria’s 190 million people are Muslims, nearly all of them Sunnis.

Zakzaky has attracted an estimated 3 million followers as a preacher of Shi’ite Islam since being drawn to that branch of the faith by the 1979 revolution in Iran.

Before Zakzaky was charged, authorities ignored a court ruling that he be released, sparking protests from his followers. IMN protests have frequently been met with force.