At least 18 people have been killed and 29 others wounded in northeast Nigeria after four suicide bombers carried out separate attacks, state police said.

The first explosion on Wednesday evening took place at a prayer ground in the Muna Gari suburb of the regional capital, Maiduguri.

Other attacks followed in the same neighbourhood.

"At about 6:13pm local time (17:13 GMT), four suicide bombers - two males and two females - infiltrated Muna Gari community and detonated IED strapped to their bodies at different locations," Victor Isuku, Borno State Police Command spokesman, said in a statement.

"A total of eighteen persons including the four suicide bombers, died in the multiple explosions," he confirmed.

Isuku said those injured were rushed to the University of Maiduguri teaching hospital and the State Specialist Hospital for medical attention.

According to the statement, police patrol and bomb disposal teams promptly mobilised to the scene to sanitise and render the area safe.

The statement also said that order had been restored to the community.

No group has yet claimed responsibility for the attacks.

'Fight is still ongoing'

The city of Maiduguri is an epicentre of activity for the armed Boko Haram group, which launched its campaign in northeast Nigeria eight years ago.

Al Jazeera's Ahmed Idris, reporting from the Nigerian city of Lagos, said although Boko Haram did not claim responsibility, "it looked like a coordinated attack by the armed group".

"What we are hearing now is that funeral services for those who have been killed in the attack are being held in Maiduguri," he said.

The UN estimates that 20,000 people have been killed and at least 1.7 million displaced since Boko Haram's offensive in 2009.

Nigeria's military has stepped up its operations against the group, but counter attacks are also on the rise in the northeast.

In early September, Amnesty International published a report that said Boko Haram was responsible for at least 400 deaths since April.

More than half of all schools in Borno are closed with millions of children unable to start classes this year because of the ongoing threat of Boko Haram, according to United Nations Children's Fund (UNICEF).

"The fight is still ongoing," said our correspondent.

"It is difficult to say at the moment what is exactly on the ground, but the military has said its operation is continuing and Boko Haram, on its part, is not relenting."