Suicide bombers linked to the Islamic State (ISIS/ISIL) affiliate Boko Haram have reportedly killed up to nineteen people and wounded 23 others in a spate of attacks that targeted a civilian self-defense force and the people who gathered to mourn their deaths in the northeastern Nigerian city of Maiduguri, known as the birthplace of the jihadist group.

Local police have deemed the attack the deadliest in months in Maiduguri, the capital of Nigeria’s Borno State, reports the Associated Press (AP).

AP notes:

Borno state police commissioner Damian Chukwu said 23 others were wounded in Tuesday night’s attacks. The police commissioner said 12 of the dead were members of a civilian self-defense force and the other seven people had been mourning them.

Meanwhile, Reuters cites a lower casualty estimate (17 killed and 21 injured), adding that no one has yet claimed responsibility for the attack.

The news outlet does acknowledge that “Maiduguri is the capital of the Nigerian state worst affected by the eight-year-old insurgency by Islamist militant group Boko Haram.”

Reuters quotes Chukwu as saying the four suicide bombers were among the 17 fatalities.

AP learned from Danbatta Bello, a spokesman for the self-defense civilian force, that at least one of the attackers was female.

Boko Haram is increasingly using girls and young women to carry out suicide attacks in Nigeria.

“Some young women who escaped extremist group have said girls are drugged and forced to carry out suicide missions,” notes AP.

The recent incident is the latest in a series of suicide bomb attacks in Maiduguri in the last few weeks.

Since 2014 alone, Boko Haram has executed 680 members of the Civilian Joint Task Force (CJTF) in Borno, considered the epicenter of the war against the terrorist group, according to Vanguard.

The vast Sambisa Forest, which covers the northeastern Nigerian states Borno, Yobe, Gombe, Bauchi, and Kano, has been identified as the organization’s primary stronghold.

Although the Nigerian military has repeatedly claimed to have killed Abubakar Shekau, the leader of Boko Haram, he keeps resurfacing in propaganda videos threatening Nigeria and neighboring countries.

Last year, the Nigerian armed forces alleged that Boko Haram had been “crushed” and driven out of the Sambisa Forest, but deadly attacks have continued to afflict the people of Nigeria.

Boko Haram has suffered some setbacks at the hands of the U.S.-backed Nigerian military.

“The group has been pushed out of most of a swathe of land around the size of Belgium that it controlled in early 2015 by the Nigeria’s army and troops from neighboring countries in the northeast Nigeria,” notes Reuters. “But insurgents continue to carry out suicide bombings and raids in northeast Nigeria, as well as in Cameroon and Niger.”

Boko Haram has reportedly killed more than 20,000 people and displaced an estimated 2.7 million in its bid to create an Islamic state.