Buhari said this while fielding questions from newsmen at the closing of the second Regional Security Summit in Abuja.
The president said the claim that the Boko Haram group was getting its arms and ammunition from IS remained unsubstantiated.
He said a major source of the group’s sophisticated weaponry was from the various military and police bases attacked at the peak of the insurgency in the affected countries.
Buhari was categorical in his submission that no clear evidence had shown that Boko Haram sourced its sophisticated weapons from IS.
“The type of weapons they are using, I believe were the ones taken from military bases they attacked at the peak of the insurgency especially in Nigeria.
“If you recall they attacked military bases and carted away weapons, they attacked police stations and broke into their armouries, that was how they got the kind of weapons they have been using to fight.
“Frankly, up till now we don’t have firm intelligence of what IS has been able to send to Boko Haram in terms of weapons or even money.
“But the fact that they said they are affiliated to IS has made many people to believe that they were getting weapons from ISIS,’’ he said.
Buhari allayed fears that members of the Civilian Joint Task Force (JTF) helping in the counter-insurgency operation in the North East would constitute threat to security in their various communities.
He said the Civilian JTF were carefully constituted by the various state government, stressing that there was a broad plan to rehabilitate them in government’s post insurgency programme.
In a related development, some representatives of foreign governments and international organisations have pledged their continued support for the Lake Chad basin counter-terrorism effort.
They stressed the need for the international community to close ranks with countries of the Lake Chad basin to tackle the root causes of terrorism and the general development of the region.
The United Kingdom’s Minister of Foreign and Commonwealth Affairs, Mr Philip Harmmon said his country had committed a lot of resources in tackling terrorism in the Chad Basin and Nigeria in particular.
Harmmon said UK would improve its support for Nigeria’s counter-terrorism efforts through intelligence sharing, training of members of the armed forces and supply of military hardware.
On his part, the United States Deputy Secretary of State, Mr Anthony Blinken said the United States had been supportive of Nigeria’s counter-terrorism war in the past two years.
He pledged the US’s commitment to improved support to the Nigerian military and to the government’s post insurgency plan.
Blinken said more military would be supplied to Nigeria to counter Boko Haram and to help in sustaining the gains that have been recorded in the war against insurgency.
He however warned that the battle against terrorism was far from over as much would be required to win the war as well as the peace.
The Vice President of the European Union, Mrs Federica Mogherini said the EU had committed 50 million Euros to support the Multi National Joint Task Force.
He said the EU remained committed to the peace process in the Lake Chad region as well as the resuscitation of economic and social activities in the region.
Presidents of France, Senegal, Niger, Chad, Gabon, Cameroon as well as representatives of other partners attended the summit.