Islamist militants from the Boko Haram terror group killed at least 15 civilians Wednesday night in coordinated attacks including three female suicide bombers in the large city of Maiduguri in northeastern Nigeria.

The militants launched their assault on the city’s suburbs with anti-aircraft guns and suicide bombers, said Damian Chukwu, the police commissioner for Borno State. The attack was the most deadly assault by the Boko Haram group in the past year.

At least 14 people were killed in three suicide bombings while another was slain by gunfire in the Jiddari Polo district as local residents tried to flee the assailants.

One of the three suicide bombers detonated her explosive belt as Muslims were leaving the mosque in the Goni-Kachallari neighborhood, killing herself along with six other people.

A second bomber blew herself up near the offices of the Development Authorities of Lake Chad at 9:20pm, killing three people in addition to the suicide bomber herself.

The third suicide bombing killed one more plus herself, and the three bombings injured an additional 24 people.

According to testimonies from eyewitnesses, a group of Boko Haram militants began the attack on the camp of Aridawari, on the outskirts of Maiduguri, around 5:00pm.

“The attackers arrived in the village carrying heavy weapons and began firing at the houses,” said Musa Umara, a resident of Aridawari. Local citizens “fled in all directions,” he added.

The insurgents then traveled to a military base across the Jiddari-Polo district, shooting at random, according to one resident, Salihu Abdallah. “The soldiers stopped them at the Giwa military barracks around 6:30pm,” he said.

The attacks on the capital city of Borno State took place a day before the interim president Yemi Osinbajo was to inaugurate an important humanitarian project to help feed 1.8 million displaced persons in the area.

Aid agencies have estimated that some 1.4 million people are affected by an emergency food shortage in the region, with 44,000 people close to starvation.

Last month, one of five Islamist militants released from prison in exchange for 82 high school girls from Chibok, had threatened to carry out a large-scale attack on Maiduguri in a video.

The liberation of the Chibok girls, abducted more than three years ago by Boko Haram, as well as the restoration of peace in the Lake Chad district were priorities set by President Muhammadu Buhari on taking office in 2015. Buhari is currently on sick leave in London.

Wednesday’s assault comes six months after President Muhammadu Buhari said that Boko Haram had “technically” been defeated, after armed forces forced many of the militants into the remote Sambisa forest, near the border with Cameroon.

Boko Haram, which pledged its allegiance to the Islamic State in 2015, has been responsible for more than 20,000 deaths and 2.6 million displaced persons since the beginning of this insurrection in 2009, according to reports.

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