Calls for secession have become increasingly loud in the last few months in parts of the southeast, where the president is deeply unpopular, prompting Buhari to say he will not allow Nigeria to be divided by separatist groups.

A million people died in a 1967-70 civil war over the short-lived Republic of Biafra. Buhari, a 74-year-old former military ruler who took office in May 2015, fought in the war as a young soldier on the government side.

The spokesman, Garba Shehu, said the president would, as part of his trip, visit the campaign run by his All Progressive Congress party in the state of Anambra ahead of gubernatorial elections in the next few days.

"Mr President will be visiting two southeast states of Ebonyi and Anambra," said Shehu. He said Buhari would leave the capital, Abuja, on Tuesday morning and return the following day.