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 bomber detonated during a marriage celebration in the northeastern town of Gwoza, Barkindo Saidu, director-general of the Borno State Emergency Management Agency, told reporters.

“Minutes later, another blast occurred near General Hospital,” Saidu said, and the third bomber at the funeral service was disguised as a mourner. Children and pregnant women were among those killed. At least 30 others were wounded, and Saidu said injuries included abdominal ruptures and skull fractures.

No one immediately claimed responsibility for the the attacks. Borno state has been heavily affected by the insurgency launched in 2009 by the Boko Haram Islamic extremist group.

In the past, Boko Haram has used women and girls in suicide bombings, prompting suspicions that some attackers come from the many thousands of people the extremists have kidnapped over the years, including schoolchildren.

Nigerian President Bola Tinubu in a statement called the attacks “desperate acts of terror” and “an isolated episode."

The insurgency, 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, with 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.

The resurgence of suicide bombings in Borno raised significant concerns about the security situation in the region.

Authorities imposed a curfew in the city. Gwoza is a few kilometers from Chibok, 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 Nigeria as armed groups find the practice a lucrative way to fund their criminal activities and take control of villages.