The deadly clashes were occurred in capital Abuja on Monday when security forces attacked a group of pro-Zakzaky peaceful protesters and opened fire on them using live bullets.
Reports, citing eyewitnesses, said at least one of the victims was an underage boy, adding that a large number of others sustained varying injuries in the brutal police raid.
The Islamic Movement in Nigeria (IMN), led by Sheikh Zakzaky, was the organizer behind the protest rally, the latest in a series of demonstration for the release of the top Shia cleric.
Zakzaky, now 66, has been in detention since December 2015 after his residence in the city of Zaria was raided by Nigeria’s forces, during which he was beaten and lost vision in his left eye.
During the brutal arrest, three of his sons were also killed, his wife sustained serious wounds, and more than 300 of his followers were killed.
Zakzaky was charged in April 2018 with murder, culpable homicide, unlawful assembly, disruption of public peace, and other accusations. He has pleaded not guilty, vehemently rejecting all accusations brought up against him.
Recent reports said that his health has been deteriorating, but prison authorities have prevented him from getting much-needed treatment.
Earlier this month, Zakzaky's son said after visiting him that he had been shocked by his father’s worsening medical condition, stressing that he needed to be immediately hospitalized as “large and dangerous quantities of lead and cadmium have been found in his blood.”
He added that Nigerian authorities had not taken any action so far and that they intended to murder his father.
In 2016, Nigeria’s federal high court ordered Zakzaky’s unconditional release from jail following a trial, but the government has so far refused to set him free.