About 500 children aged 11 and under are missing from a Nigerian town recaptured from militants, a former resident of Damasak has told the BBC.
A trader in the north-eastern town told Reuters news agency that Boko Haram fighters took the children with them when they fled.
Troops from Niger and Chad seized Damasak earlier in March, ending months of control by the Islamist militants.
A regional force has recently been helping Nigeria take on the insurgents.
Thousands have been killed since 2009, when Boko Haram began its insurgency to create an Islamic state.
The senator representing the north of Borno state, Maina Maaji Lawan, told the BBC's Nigeria correspondent, Will Ross, the case in Damasak was typical and many hundreds of children are missing.
He said: "The very young ones they give to madrassas… and male ones between 16 and 25, they conscript them and they indoctrinate them as supply channels for their horrible missions."
Boko Haram caused international outrage in April 2014 after it abducted more than 200 girls from a boarding school in Chibok town in north-eastern Nigeria's Borno state.
The group's leader Abubakar Shekau has said the girls have been married off.
Damasak is a trading town in Borno state near Niger's border and is about 200km (120 miles) from the state's main city of Maiduguri.
It was overrun by the militants at the end of last year.
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