A teenage girl strapped with explosives ran away from a crowded mosque this week, killing only herself and cementing suspicions that Boko Haram is using unwilling captives in its terror campaign in northeast Nigeria.

The girl took off after her companion blew up in an explosion that killed 30 people on Monday in Maiduguri, the biggest city in northeast Nigeria, witnesses and a mortuary worker said.

"In the confusion of the blast, the other girl just ran away and only exploded when she was far from the crowd," said fishmonger Idi Idrisa.

It was unclear if the teenager fled in fright, fear or on purpose, but this and other bungled bombings have many believing that Nigeria's home-grown Boko Haram Islamic extremist group is using some of its thousands of kidnap victims as unwilling weapons.

A military bomb disposal expert has told The Associated Press that most bombs carried by girls and women have remote detonation devices, meaning the carrier cannot control the explosion.

The U.N. children's agency last month reported an "alarming spike" in suicide bombings by girls and women, saying the number of reported suicide attacks had jumped to 27 in the first five months of this year compared to 26 for all of last year.

On Monday, a girl who looked no more than 12 years old detonated explosives that killed 10 people and injured 30 in a crowded market at Wagir village in northeastern Yobe state, according to truck driver Malam Usaini Jibril.

This past week, at least 85 people have been reported killed in suicide bombings and village attacks blamed on Boko Haram. Hundreds of homes have been burned.

Victims include five villagers killed in a cross-border raid in the Diffa region of neighboring Niger.

Niger's army responded with an attack that killed 16 suspected Boko Haram militants and captured 32, according to a government statement.

"The war against Boko Haram is a non-negotiable political goal," Niger's government said in a statement read on state television Thursday night. "The fight against Boko Haram will give us our collective freedom."

The United States has condemned the attacks and promised support for a multinational army that this year has driven Boko Haram from a large swath of northeast Nigeria where it had set up a so-called Islamic caliphate under its harsh version of Shariah law.

But the multinational fight has been bogged down with Chad claiming it has had to retake some towns two and three times because Nigerian troops have not arrived to secure them.

Underscoring those failures, the U.S. Embassy this week said "We encourage the government of Nigeria to take steps to secure and govern liberated areas by filling in behind military successes with police and civilian administration."

Boko Haram says Western-style democracy has brought only corruption and inequality to oil-rich but impoverished Nigeria and that only Islamic rule offers a just solution in the country of about 170 million people almost equally divided between Christians and Muslims.

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Abdulaziz reported from Yola, Nigeria. Associated Press reporters Dalatou Mamane in Niamey, Niger and Michelle Faul in Lagos, Nigeria, contributed to this report.