Abba Kyari had acted as the gatekeeper to 77-year-old President Muhammadu Buhari. After his re-election last year, Buhari ordered ministers to channel all communications through him.
Kyari had underlying health problems including diabetes. His age was not officially disclosed, although two presidency aides said he was 70. Reuters reported on March 24 that he had contracted the disease.
"The deceased had tested positive to the ravaging COVID-19, and had been receiving treatment. But he died on Friday, April 17, 2020," presidency spokesman Garba Shehu said in a tweet.