He said he would deploy all appropriate and legal measures to rid the country of graft.
Buhari made the promise in his Eid el-Fitr message to Nigerians.
The message personally signed by the President was made available to journalists on Tuesday.
“Let me also use this opportunity to reaffirm that we will not relent in the fight against corruption and we will ensure that all appropriate and legal measures are deplored to root out this malaise,” the President promised.
Buhari who said he was aware of the difficulties Nigerians are going through, commended what he called their amazing sacrifices in the face of the temporary economic and social challenges.
He reassured them that his administration is working assiduously towards providing basic needs and other amenities.
The President also commended the Armed Forces and other security agencies for the gains recorded in the fight against terrorists and the rescue of hostages in the North East part of the country.
He added, “I also appeal for the support, understanding and patience of all Nigerians and our international partners as we explore the fastest means to end the economic sabotage in the Niger Delta and amicably resolve the conflicts within the region.
“I promise you all better days ahead even as we remain grateful for your unflinching support to our administration.”
While felicitating with all Nigerians, especially the Muslim Ummah, on this year’s Eid el-fitr, Buhari prayed that the Almighty Allah would reward their sacrifices with increased blessing and a more prosperous future.
As they celebrate, he urged them to continue to imbibe the virtues of piety, sacrifice, love, self-denial and good conduct in their daily relationship with one another which they had learnt during Ramadan.
The President also urged Nigerians to learn to show gratitude, respect and tolerance to one another, irrespective of their religion, tribe, language and political leanings, as they forge ahead to build on their strengths and opportunities to make Nigeria great again.
He added, “On Monday this week, the Vice-President, the Speaker of the House of Representatives and other government officials joined me to host Iftar reception at the State House with Nigerians of different backgrounds including Internally Displaced Persons, artisans and physically-challenged persons.
“Like I said during the reception, I want to once again appeal to those of us who have the means, to remember the millions of Nigerians who are suffering deprivation because of violence perpetrated by terrorists.”