Boko Haram militants are suspected to have killed dozens of people in five attacks on Nigerian villages after a government-announced cease-fire to enable 200 abducted girls to be freed, security sources and witnesses said Saturday.

However, the government cast doubt on whether the attacks really were by Boko Haram or one of several criminal groups that are exploiting the chaos of the insurgency. A spokesman said talks to free the girls would continue in Chad on Monday.

The fresh attacks dashed hopes for an easing of the northeast’s violence, although officials remained confident they can negotiate the release of girls whose abduction by the rebels in the remote northeastern town of Chibok in April caused international shock and outrage.

Government sources said they were aiming to do this by Tuesday.

Boko Haram, whose name translates roughly as “Western education is sinful,” has massacred thousands in a struggle to carve an Islamist state out of religiously mixed Nigeria, whose southern half is mainly Christian in faith.

The 200 Nigerian schoolgirls kidnapped six months ago by Islamist militant group Boko Haram may soon be released following a cease-fire deal. (Reuters)

Nigeria’s armed-forces chief, Air Chief Marshal Alex Badeh, announced the cease-fire on Friday. On Saturday, two senior government sources said Nigeria aims to secure the girls’ release as early as Monday or Tuesday, although they declined to give further details.

When asked about the attacks on the villages, government spokesman Mike Omeri said by telephone that “the Boko Haram people have also said that some attacks are not undertaken by them.”

Boko Haram, seen as the biggest threat to Africa’s top economy and oil producer, is believed to be divided into several factions that loosely cooperate with each other, and it is unclear with which faction the government has been negotiating.

“Discussions will continue in Chad next week, and on the basis of those discussions we’ll have more details” on how the girls will be released, Omeri said.

Boko Haram has not commented on the reported truce. The group’s sole means of conveying messages is via videotaped speeches by a man claiming to be it’s leader, Abubakar Shekau, whom the military last year said it had killed.

A history of abortive government attempts at truce deals with Boko Haram, along with military claims to have rescued some girls that proved false, mean Nigerians are likely to greet the newly reported breakthrough with skepticism.

— Reuters