The Islamist militant group Boko Haram has been active in north-eastern Nigeria for well over a decade.
President Buhari says its activities have been largely brought under control since he assumed office in 2015.
His political opponents disagree and say the situation has recently deteriorated both in terms of the number of attacks and kidnappings by the group.
Ahead of Nigeria’s elections on 16 February, BBC Reality Check examines the competing claims over the security situation in the country.
What is Boko Haram?
Formed around 2002 as a non-violent organisation with the aim of purifying Islam in northern Nigeria, it became increasingly radicalised and eventually adopted militant tactics in pursuit of its aims.
It has been active not only in Nigeria, but also in the neighbouring countries of Chad, Niger and Cameroon.
Tens of thousands of civilians have been killed and more than two million displaced over the past decade.
Boko Haram has been notorious for kidnapping schoolchildren and attracted global media attention in 2014 following the abduction of almost 300 girls from a school in the town of Chibok, in Borno, the state where the militant group has been most active.