National Security Adviser Babagana Monguno on Monday dismissed any "illusion" about heightened insecurity, including warnings by U.S. officials of possible terror attacks.
"It is false, it is irresponsible for anybody to give that signal," he told reporters.
"We are working with our foreign partners in a responsible way and Nigerians should go back to their normal daily undertakings without being put in a situation of fear."
U.S. security concerns prompted Washington to take non-essential personnel and families out of its embassy in Abuja.
Nigerian police say they have increased security since the US warning, but Buhari last week urged calm and said there was no threat of an imminent attack on Abuja.
The Nigerian president was Lond0n-bound Monday for medical appointments.
Buhari, who has made repeated trips overseas for checkups and treatment for an undisclosed ailment, steps down next year after two terms in office.
Security will be a major theme in the February 2023 election to replace the former military commander who was first elected in 2015 largely on his promise to defeat jihadists and armed groups.
Nigeria's overstretched military is battling jihadists, criminal gangs and separatist groups in different regions of Africa's most populous country.
Islamic State West Africa Province [ISWAP] and Boko Haram are mostly active in the country's far northeast, but jihadists have recently claimed attacks in other areas and closer to the capital Abuja.
In July, ISWAP claimed a brazen attack on Kuje prison just 40 kilometers from the Nigerian capital, freeing hundreds of prisoners including suspected militants.