The warning was made during an Iftar dinner with diplomats on Thursday at the president's residence in the capital, Abuja.

Presidential elections are scheduled for February 2023.

"As Nigeria goes through this trajectory, I urge our friends in the global community, represented by you the diplomatic corps, to adopt a positive role that reinforces the doctrine of respect for our internal affairs and respect for facts and devoid of pre-conceived notions and bias," Mr Buhari is quoted as saying in a statement.

He also vowed to crack down on electoral fraud.

"Those planning to rig the forthcoming elections should think twice because I intend to resolutely protect and defend the sacred will of the Nigerian people, to be expressed through the ballot box," he said.

Mr Buhari's second term ends in May 2023 and he is not eligible for re-election.