A girl believed to be about 10 years old was strapped with explosives and sent into a busy market in Nigeria on Saturday, killing at least 16 and injuring more than 20.

The blast, in the city of Maiduguri, occurred in an area of Borno State where the Islamist group Boko Haram has been wreaking havoc for more than five years.

“The explosive devices were wrapped around her body and the girl looked no more than 10 years old,” a police source told Reuters.

The bombing took place just days after one of the worst Boko Haram attacks ever. Some 2,000 people are believed to have been gunned down in the town of Baga, also in Borno.

Agence France-Presse quoted Ashiru Mustapha, described as a “civilian vigilante,” saying the blast Saturday happened as the girl was searched at the entrance to the market. “The girl was about 10 years old and I doubt if she actually knew what was strapped to her body,” Mustapha said.

“In fact, she was searched at the entrance of the market and the metal detector indicated that she was carrying something,” he told AFP. “But sadly, the explosion went off before she was isolated, killing at least 10 people and injuring many others.”

Forced conscription of children by Boko Haram has been reported by Human Rights Watch since November 2013. At that time, the group reported the abduction of a number of young girls selling goods on the streets or working on farms in remote villages. It said Boko Haram used children as young as 14 in its numerous attacks on villages in Nigeria.

In December, a 13-year-old girl named Zarau Babangida from Yobe State in Nigeria offered a chilling account after her arrest of how her parents volunteered her services to Boko Haram, which then sent her and other children into a village strapped with explosives. She told In Depth Africa:

When my parents took me to the Boko Haram training camp in Bauchi, I did not have an idea what they wanted me to go and do. But when we got there, one of the trainers asked me whether I wanted to go to paradise. I replied in the affirmative. He then told me that I had an assignment to carry out in Kano. After the necessary training, he told me that three of us (all female) would travel to Kano to execute the assignment, saying after executing the assignment, we would then be entitled to make it to paradise.

When we got to Kano, they took us straight to Kantin Kwari market. When it was time for the execution, the two other girls took their position. We all had the bombs concealed in our dresses because we were wearing hijab. The others detonated their bombs, but I vehemently refused to ignite mine. But I was injured on my left leg from the explosion.

Zarau was in police custody as she spoke, according to the news report.