Iran urges Nigeria to provide Sheikh Zakzaky with prompt medical care.
'Nigerian authorities are expected to take immediate measures to transfer Sheikh Zakzaky out of detention and provide him with appropriate and prompt medical services,' Mousavi said on Tuesday, Mehr reported.
Mousavi also expressed deep concerns about the recent unrest in Nigeria's capital, Abuja, and condemned the government's use of force against protestors.
He underlined the need to ensure security and peace in Nigeria and called on the government to observe tolerance toward the protestors.
On Monday, Nigerian security forces killed at least six protesters who were demanding the immediate release of Sheikh Zakzaky, who has been locked up in a government jail since 2015.
The deadly clashes occurred in Abuja, where security forces attacked a group of pro-Zakzaky protesters and opened fire on them using live bullets.
The Islamic Movement in Nigeria (IMN), led by Sheikh Zakzaky, was the organizer behind the protest rally, the latest in a series of demonstrations for the release of the top 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.