Abba Kyari is the highest-profile person in Nigeria to be killed by a virus that has caused 493 confirmed infections in the country and 17 deaths.
The powerful chief of staff to Nigerian leader Muhammadu Buhari has died after contracting the novel coronavirus, the presidency said on Saturday.
Buhari's office announced in a statement that it "regrets to announce the passage" of Abba Kyari, who acted as gatekeeper to the president of Africa's most populous nation.
"The deceased had tested positive to the ravaging Covid-19, and had been receiving treatment. But he died on Friday, April 17, 2020," the statement said.
"May God accept his soul."
Kyari, whose exact age has never been officially confirmed but who was believed to be in his seventies, is the highest-profile person in Nigeria to be killed by a virus that has caused 493 confirmed infections in the country and 17 deaths.
He was buried in Abuja on Saturday in the presence of his family and close friends wearing traditional dress, as well as masks.
The influential technocrat, who was reported to have suffered from underlying health issues, was seen as one of the dominant figures in the tight-knit group of advisors around Buhari.
He reportedly controlled access to the president, a 77-year old former military ruler now in his second term as democratically elected leader, overseeing key meetings and granting ministers audiences.
"His death will have an enormous impact," a European diplomatic source told AFP on Saturday.
"He really was a strong force who had a key influence. Without him, there will be a vacuum for a while. Political decision-making will perhaps be a little slower," the source said, speaking on condition of anonymity.
'De facto head of government'
The Nigerian newspaper, Daily Trust, wrote in a leader column that "his closeness to the president and Buhari's unshakable trust in him saw Kyari become the de facto head of government, especially since the president handed him a free reign."
That led to accusations "that he had the president in a golden cage," the newspaper said.
Kyari tested positive for coronavirus in late March after visiting Germany, forcing a string of top Nigerian officials who had been in contact with him to self-isolate.
In a statement released on March 29, Kyari said he had been transferred to Nigeria's biggest city Lagos for private medical treatment and hoped "to be back at my desk very soon".
There has been no official confirmation on whether Buhari has taken a test, but the president has since made repeated televised speeches imposing restrictions to curb the spread the virus.
The central government has imposed a lockdown on Nigeria's economic hub Lagos and capital Abuja, while state governors have ordered a raft of measures in other regions.
Experts say the country of 200 million is highly vulnerable to the spread of the disease given its weak healthcare system and high population density.