LAGOS, Nigeria (AP) — Police say three suicide bombers have attacked a crowded market in northern Nigeria, killing at least 18 people.

Borno state police spokesman Joseph Kwaji confirms the Friday night attack to The Associated Press.

The bombers, all believed to be female, left another 22 people wounded at a fish market Konduga, just outside the state capital, Maiduguri.

The Islamist extremist group Boko Haram continues to carry out deadly suicide bombings in Borno and other parts of northern Nigeria as part of its violent campaign to establish an Islamic state in the West African nation.

The extremist group has increasingly used women and youth as bombers, often after abducting and indoctrinating them.

Maiduguri is the birthplace of the extremist group and has been a frequent target.