POTISKUM, Nigeria — A girl as young as 10 blew herself up in a busy market in northeastern Nigeria, killing herself and four others, and fueling fears Islamic extremists are using kidnapped girls as suicide bombers.

There was no immediate claim of responsibility for the attack Sunday, which also seriously wounded 46 people, but it bore the hallmarks of Nigeria’s homegrown extremist group, Boko Haram.

The girl, who appeared to be no more than 10 years old, got out of a tricycle taxi in front of the busy cellphone market in Potiskum and minutes later her explosives detonated, according to Anazumi Saleh, a survivor of the attack who suffered head injuries.

Authorities were not immediately able to confirm the girl’s identity or her precise age from her remains.

In recent months, Boko Haram has begun using teenage girls and young women for suicide bombings in marketplaces, bus stations and other busy areas, but the girl in Sunday’s attack appeared far younger. It is not clear whether the girls and women have set off the explosions themselves, or whether the detonations were controlled remotely.

Boko Haram, whose name means “Western education is sinful” in the local Hausa language, attracted international condemnation when its fighters kidnapped 276 mostly Christian schoolgirls from a boarding school in the northeastern town of Chibok in April. Dozens escaped but 219 remain missing. Boko Haram has said the girls have converted to Islam and been married off to extremist fighters.

Boko Haram’s violent campaign in Nigeria killed at least 10,000 people last year, according to the Council on Foreign Affairs. At least 1.6 million people have been driven from their homes in the group’s brutal five-year uprising to create an Islamic state in Nigeria, Africa’s most populous nation of 160 million people divided between mainly Muslims in the north and Christians in the south.