MAIDUGURI, Nigeria — Female suicide bombers targeted a wedding, a funeral and a hospital in coordinated attacks in northern Nigeria that killed at least 18 people, local authorities said Sunday.

The first suicide bomber detonated an explosive device during a marriage celebration in the northeastern town of Gwoza at about 3 p.m., Barkindo Saidu, director-general of Borno State Emergency Management Agency, told reporters.

“Minutes later, another blast occurred near General Hospital,” Saidu said, and then there was a third attack at a funeral service by a female bomber disguised as a mourner. Children and pregnant women were among those killed.

No one has so far claimed responsibility for the the attacks, but Gwoza is in Borno state, which has been heavily impacted by an insurgency launched in 2009 by Boko Haram, an Islamic extremist group.

The violence, which has spilled across borders around Lake Chad, has killed over 35,000 people, displaced over 2.6 million and created a massive humanitarian crisis.

Boko Haram, which has one branch allied to the Islamic State group, wants to install an Islamic state in Nigeria, West Africa’s oil giant of 170 million people divided almost equally between a mainly Christian south and a predominantly Muslim north.

In the past, Boko Haram has used women and girls in suicide bombings, prompting suspicions that some from the many thousands that they have kidnapped over the years. The resurgence of suicide bombings in Borno raises significant concerns about the security situation in the region.

Saidu said the degree of injuries ranged from abdominal ruptures to skull and limb fractures.

“I am now coordinating for a chopper tonight,” Saidu said.” I have mobilized emergency drugs to complement the shortage of drugs in Gwoza.”

Authorities imposed a curfew in the city, and the community remained on a high alert following reports of another suspected bomber in Pulka, a town about 2 kilometers (just over a mile) away from Gwoza.

Gwoza is located a few kilometers from Chibok, in southern Borno, where 276 schoolgirls were abducted in 2014. Nearly 100 of the girls are still in captivity.

Since then, at least 1,500 students have been kidnapped across the country as armed groups increasingly find the practice a lucrative way to fund their criminal activities and take control of villages.