Two suicide bombers killed at least three people and injured 16 in the capital of the northeastern Nigerian state of Borno on Saturday, the latest in a string of deadly attacks by suspected Islamist militants.

The two women tried to get into a hospital but were stopped by security guards at the gate and blew themselves up, witnesses said.

"We evacuated the charred bodies of the two security guards, another civilian and the two bombers," said Auwal Mohammed, a member of the community in Molai, where the hospital is situated.

Muhammadu Buhari, the new president of Africa's most populous nation and biggest economy, made Maiduguri the command centre for the military campaign against Islamist militant group Boko Haram after being inaugurated last month.

More than 100 people have been killed in northeast Nigeria in the past few weeks in a spate of bombings, mostly in Maiduguri.

A source at the mortuary of Borno State hospital in Maiduguri confirmed it had received three corpses after the blast. Another hospital source said 16 people injured in the attack had been brought in.

Buhari has held talks with counterparts in neighbouring countries to set up a joint force to tackle the insurgents and he is planning to visit Cameroon later this month to discuss deeper collaboration.

Buhari is also due to visit U.S. President Barack Obama in Washington on July 20 and the fight against Boko Haram is likely to be high on the agenda.

Boko Haram controlled territory the size of Belgium in the northeast at the start of the year but has been pushed out of most of it by the Nigerian army, backed by troops from Chad, Niger and Cameroon.