LAGOS — A wave of violence hours after Nigeria's government announced a truce with Boko Haram raised doubt on Sunday about whether more than 200 schoolgirls kidnapped by the Islamist militants will really be released, deflating the new hopes of their parents.

Nigeria's armed forces chief Air Chief Marshal Alex Badeh announced the ceasefire on Friday to enable the release of the girls, who were abducted from the remote northeastern village of Chibok in April.

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But Boko Haram has not confirmed the truce and there have been at least five attacks since — blamed by security sources on the insurgents — that have killed dozens. Talks were scheduled to continue in neighboring Chad on Monday.

"We were jubilating. We had every reason to be happy ... but since then the ceasefire has been broken in quite a number of places already," Lawan Abana, a parent of the one of the missing girls, told Reuters by telephone.

He added that there were doubts about the credentials of the reported Boko Haram negotiator Danladi Ahmadu, who was unheard of before. "Can we trust him that he can deliver on this promise of releasing the girls when he has not delivered on the promise of the ceasefire?" Abana said.

The government says the attacks may not have been Boko Haram but one of several criminal groups exploiting the chaos of its insurgency. Analysts point out that Boko Haram is anyway heavily factionalized, so what matters is whether the faction the government is talking to has control over the girls' fate.

Campaigners from "#Bring Back Our Girls" march during a rally calling for the release of the Abuja school girls who were abducted by Boko Haram militants, in Abuja October 17, 2014. AFOLABI SOTUNDE / Reuters

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— Reuters