President Muhammadu Buhari on Wednesday criticised fellow leaders who extend term limits to cling to power, saying this was having a "corrosive" effect, and promised free and fair elections when the country elects his successor in February.

Buhari, 79, who took office after defeating a sitting president in elections in 2015, will make way for a new leader in what would be another peaceful transfer of power, helping cement Nigeria's democratic credentials in a region prone to coups.

Nigeria ended decades of military rule in 1999.

Speaking at his last United Nations General Assembly, Buhari said Africa's most populous nation had invested heavily to ensure free and fair elections.

"We believe in the sanctity of constitutional term limits and we have steadfastly adhered to it in Nigeria. We have seen the corrosive impact on values when leaders elsewhere seek to change the rules to stay on in power," said Buhari.

"As President, I have set the goal that one of the enduring legacies I would like to leave is to entrench a process of free, fair and transparent and credible elections through which Nigerians elect leaders of their choice."

Official election campaigning starts next week.

Reuters