GUBIO, Nigeria -- Children are now being seen as potential threats after an "alarming spike" in suicide bombings by girls and women used by Boko Haram militants in northeastern Nigeria, the U.N. children's agency said Tuesday.

The number of reported suicide attacks has jumped to 27 in the first five months of this year compared to 26 for all of last year, it said.

Tuesday's report came as Gov. Kashim Shettima of Borno state visited the site of the latest Boko Haram attack and surveyed the damage: 37 people killed Sunday, 400 buildings razed including mosques, and 22 vehicles and dozens of motorcycles torched.

"I appeal to you not to flee from your homes. We assure you that we are going to rebuild the ancient town of Gubio," Shettima pleaded.

But locals looking at firebomb attacks that left even the earth and trees scorched said hundreds of traumatized residents already have fled to Maiduguri, the Borno state capital 90 kilometres (55 miles) away.

A civilian self-defence fighter, Yusuf Modu Gubio, said he killed some insurgents in Sunday's attack but "to my surprise, they were mostly young boys and teenagers."

It's not known how many thousands of boys, girls and women have been kidnapped by Boko Haram but new abductions are reported every week. UNICEF said it estimates that 743,000 children have been uprooted by the nearly 6-year-old Islamic uprising, with as many as 10,000 separated from their families in the chaos.

It said women and children have carried out three-quarters of all reported Boko Harem suicide bombings -- with girls blamed for nine such attacks since July.

"Children are not instigating these suicide attacks; they are used intentionally by adults in the most horrific way," said Jean Gough, UNICEF representative in Nigeria. "They are first and foremost victims -- not perpetrators."

The agency is concerned that children will increasingly be seen as "potential threats," putting them in danger of retaliation and jeopardizing their return home.

A trauma counsellor helping some of 700 children and women rescued from captivity by Nigeria's military last month told The Associated Press he had to have a 4-year-old Boko Haram supporter removed from a refugee camp. He feared for the boy's life.

The child openly boasted that his father would slit people's throats and said the killing of infidels was the work of God, according to the counsellor, who insisted on anonymity because of the sensitivity of the subject.