Buhari said "the federal and state governments have jointly and collaboratively worked hard on how to balance the need to protect health while also preserving livelihoods, leveraging global best practices while keeping in mind our peculiar circumstances".
He also ordered new nationwide measures against Covid-19, including a night-time curfew and mandatory face masks.
Buhari said the Presidential Task Force on COVID-19 will provide specific details to allow for preparations by governments, businesses and institutions.
President Buhari had declared a two-week lockdown of Lagos, Abuja and Ogun during his first address on the pandemic on March 29 to enable the country tackle the coronavirus pandemic.
President Muhammadu Buhari announced the extended lockdown in a nationwide broadcast on Monday in which he released new measures to be taken to control the spread of COVID-19.
The government in the northern state said preliminary investigations revealed the deaths were caused by complications from hypertension, diabetes, meningitis and acute malaria.
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"I have approved a phased and gradual easing of lockdown measures in FCT, Lagos and Ogun States effective from Monday, 4th May, 2020", he said.
But the Nigerian Medical Association had advised the government to extend the lockdown by two more weeks, raising concerns a spike in the spread of the contagion if the country reopens now.
A post on the NCDC Twitter handle reads: "As at 11:20pm 27th April- 1337 confirmed cases of #COVID19 reported in Nigeria".
The moves would ensure the economy functioned "while still maintaining our aggressive response", Mr Buhari said.
The president also placed a ban on interstate passenger travel until further notice.