Maiduguri is the capital of the northeast state of Borno, the epicenter of a 12-year Islamist insurgency. The city and surrounding areas are routinely attacked by militants.

Four people were killed in Maiduguri's Gomari Ayafe area, a few hundred metres from an air force base, residents said. Buhari landed at the base less than an hour after explosions were heard in neighbourhoods near the base.

A Reuters witness saw two bodies, including that of a child and several injured people being taken to hospital in open trucks. Three houses were extensively damaged and residents suspected Islamist militants.

"We have received four dead people and 15 others injured that we have recorded," a doctor at Umaru Shehu Hospital, where the injured were taken, told Reuters.

Hussaini Garba, a resident of Ajilari Cross, another Maiduguri neighbourhood, a few kilometres from the air base said he had just left home for work when he heard a loud bang. He rushed home only to find his house badly damaged and his 18-year-old daughter lying dead.

"My house and that of my neighbours are both destroyed, nothing is left in the house," Garba said.

The military and presidency declined to comment.

Buhari did not comment on the explosions during his visit to Maiduguri to commission some projects, including a road bypass.

However, he told troops at the air base that his government was working towards "the defeat of all adversaries and restoration of an economically viable north east geo-political zone and other parts of the country where Nigerians are free to go about their activities without fear or harassment."

Nigeria is gripped by persistent insecurity, including the Islamist insurgency in the northeast and banditry and kidnappings in the north and northwest.

Reporting by Lanre Ola and Maiduguri newsroom; additional reporting by Camillus Eboh and Felix Onuah in Abuja;

Writing by MacDonald Dzirutwe; Editing by Richard Chang