"They are forcing people to join them," Jubrin Gunda, a spokesman for a local vigilante group, told The Anadolu Agency.
"It is a known fact that they force people to join them," he said. "They give people money – but if you reject the offer, they kill you."
Gunda said he had information that the insurgent group was training conscripts in camps in Gwoza, the center of Boko Haram's self-declared "Islamic caliphate," and Bama, another major town believed to be under the group's control.
"But not everyone is willing [to join Boko Haram]," he asserted.
"What they [the militants] don't understand is that once you force people to join, and such a person later has an opportunity, he will try to escape," added Gunda.
He insisted that Boko Haram had long relied on forced conscription to swell its ranks.
"But it has worsened recently, as security agencies have begun closing in," Gunda told AA. "Because of intense military operations, they are very desperate to shore up their ranks."
Gunda suggested that the military was gaining the upper hand in its fight against the militants.
He pointed to ongoing fighting in Ashigashiya, a border town between Nigeria and Cameroon, where the Cameroonian army has been pounding Boko Haram positions.
For the last five years, Nigeria has battled a fierce Boko Haram insurgency that has ravaged the country's volatile northeastern region.
A seemingly emboldened Boko Haram recently stepped up its militant activity, seizing several areas of Nigeria's Adamawa, Borno and Yobe states, where it has declared a self-styled "Islamic caliphate."
Baba Mohammad, a 61-year-old displaced by the fighting from Gwoza, confirmed the conscription reports.
"Some of our people just escaped from the Gwoza camp where they were being trained to become insurgents," he told AA.
"They told us tales of horror, killing and suffering," Mohammad added.
He said forced conscription appeared to be the only option left for Boko Haram, "since many of our youths now see through their evil intentions; people now see them as the architect of our suffering."