As many as seven suicide bombers, six of them women, have blown themselves up while trying to attack the northeast Nigerian city of Maiduguri, according to emergency services officials.

Initial reports from Maiduguri had suggested a number of people were killed in the blasts near the Muna camp for displaced people shortly before 11:30pm (22:30 GMT) on Thursday.

But Mohammed Kanar, from the National Emergency Management Agency (NEMA), said on Friday there were no civilian or military casualties, as the would-be bombers arrived after the 10pm (21:00 GMT) curfew.

"People were indoors. There was no one on the streets," Kanar, who is NEMA's northeast coordinator, told AFP news agency.

"None of the six female bombers succeeded in their attacks. They ended up being killed in the explosions."

A man who dropped them off in his car then tried to ram a military checkpoint was also unsuccessful.

"He died in the process," said Kanar, referring to the man.

Similar account

Hamed Satomi, from the Borno state emergency management agency, gave a similar account, although he said there were only six bombers.

Both organisations were involved in the recovery of the bodies, they said.

The Borno state police had earlier said only one bomber was involved and that he had detonated his explosives among 13 trucks waiting to travel to the east of the state near the Cameroon border.

Victor Isuku, police spokesman, attributed the multiple explosions heard in Maiduguri to soldiers shelling suspected Boko Haram fighters outside the city limits.

The attempted attacks came after the departure of a high-ranking delegation of foreign officials to Maiduguri as part of efforts to secure greater funding to help those made homeless by the conflict.

Reports from the city also said a number of Nigerian air force aircraft were shot at in the remote region on Thursday.

'Technically defeated'

The incidents underline the continued threat from Boko Haram, which Nigeria's military maintains is in disarray after nearly eight years of fighting and at least 20,000 deaths.

Despite the insistence that Boko Haram is "technically defeated", there have been multiple suicide bombings against civilian targets, as well as attacks on police and soldiers.

The thousands of people living at the Muna Garage camp are especially vulnerable, given the lack of security and easy access to the site.

A multinational force of troops from Nigeria and its neighbours last year drove Boko Haram out of towns and villages in northeast Nigeria, but isolated attacks and suicide bombings continue.

In December, President Muhammadu Buhari said the capture of a key camp marked the "final crushing" of Boko Haram in its last enclave in Sambisa Forest, once the group's stronghold.

But since then, the group, which split into two factions last year, has stepped up its attacks.

One Boko Haram faction is led by Abubakar Shekau from the Sambisa Forest. Abu Musab al-Barnawi leads the other faction, based in the Lake Chad region, which allies itself to Islamic State or Iraq and the Levant (ISIL) group.

Boko Haram's seven-year armed campaign has killed 15,000 people and forced up to two million from their homes.