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.

No one immediately claimed responsibility for the the attacks in Borno state, which has been heavily affected by the insurgency launched in 2009 by Boko Haram. The extremist group previously has used women and girls in suicide bombings, prompting suspicions that some attackers come from the many thousands of people the militants have kidnapped over the years, including schoolchildren.

The first suicide bomber detonated a device 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.

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

The insurgency, which has spilled across borders around Lake Chad, has killed more than 35,000 people, displaced 2.6 million others and created a 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.