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.

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.