Boko Haram Nigeria North
Policemen stand near damaged vehicles in Sabon Gari, Kano, after a Boko Haram car bomb attack killed five earlier this year.Reuters

Two female suicide bombers have detonated devices in a crowded market in the northeastern Nigerian city of Maiduguri, according to witnesses and police.

A local health worker told AFP news agency that at least 45 people were killed in the explosions but no official confirmation of the death toll has been released.

Health worker Dogara Shehu said that he saw over "45 people killed, some of them completely decapitated" in figures supported by a witness, who wished not to be named.

The two teenager girls were dressed in full Islamic hijabs and detonated their explosives amid customers at the market, according to Abba Aji Kalli, the Borno state coordinator of the Civilian Joint Task Force (CJTF).

"I am right here at the scene and I have before me 11 corpses ... many have been taken away by relatives, while others are taken to the state specialists' hospital," said Kalli.

Eyewitness and vendor Hajja Asamau told AFP news agency that she saw "four people in the ground in a pool of blood".

No group has yet claimed responsibility for the blast but suspicion will fall on the Islamist militant group Boko Haram as Borno State is a stronghold of theirs and they have conducted a number of attacks on the city and the surrounding area.

Borno has been placed under a state of emergency since May last year because of the terror group's insurgency, along with the states of Yobe and Adamawa.

According to Human Rights Watch, the militants have killed at least 2,053 people since the beginning of 2014, but researchers at the John Hopkins University School of International Studies estimate that 7,000 people have been killed in the 12 months between July 2013 and June this year.