El-Zakzaky who is in the custody of the Department of State Services (DSS), told journalists on Saturday in Abuja that he is alive and well.
He also thanked Nigerians for their prayers, as well as the DSS for allowing him access to his doctors.
“It was severe on me on Monday but subsequently it started subsiding and for the first time at least the security allowed me to see my own doctors.
“So it was my own doctors who examined me. Before I used to be examined by security doctors, this time I did not agree, and my own doctors came to examine me.
“I am getting better, thanks to all your prayers,” the IMN leader said.
This comes after rumours of his death spread on the social media on Friday.
Despite the ruling of a Federal High Court which ordered his unconditional release in 2016, Mr El-Zakzaky and his wife have remained in detention since December 2015.
Their continued detention has sparked several reactions from his supporters, the government and even human rights lawyer, Femi Falana.
Members of the IMN group also known as Shiites have staged series of processions across the northern states demanding the release of their leaders.
Speaking on the issue, the Minister of Information, Culture and Tourism, Mr Lai Muhammad stated earlier that Mr El-Zakzaky was still being held on the grounds of national security.
He also noted that contrary to reports, the Shiite leader was not in prison, the Department of State Services or police custody but was rather in protective custody with his family.