Nigeria's government and Islamic extremists from Boko Haram have agreed to an immediate cease-fire, officials said Friday.

The fate of more than 200 missing schoolgirls abducted by the insurgents six months ago remains unclear. Defense Ministry spokesman Maj. Gen. Chris Olukolade said their release is still being negotiated.

Boko Haram negotiators "assured that the schoolgirls and all other people in their captivity are all alive and well," Mike Omeri, the government spokesman on the insurgency, told a news conference.

The chief of defense staff, Air Marshal Alex Badeh, announced the truce and ordered his troops to immediately comply with the agreement.

"Already, the terrorists have announced a cease-fire in furtherance of their desire for peace.  In this regard, the government of Nigeria has, in similar vein, declared a cease-fire," Omeri said.

There was no immediate word from Boko Haram, which limits its announcements almost exclusively to videos of its leader Abubakar Shekau.

It could take days for word to get to fighters of Boko Haram, which is broken into several groups. They include foreigners from neighboring countries Chad, Cameroon and Niger, where the insurgents also have camps.

There have been unconfirmed reports that at least some of the girls have been carried across borders, and some forced to marry their captors. A Boko Haram video in May showed two of the girls explaining why they had converted from Christianity to Islam.

Omeri confirmed there had been direct negotiations this week about the release of the abducted girls. Another official said the talks took place in neighboring Chad. He spoke on condition of anonymity because he is not authorized to talk to reporters.

Boko Haram had been demanding the release of detained extremists in exchange for the girls. President Goodluck Jonathan originally said he could not countenance a prisoner swap.

Boko Haram -- the group's nickname means "education is sinful" -- attracted international condemnation with the April 15 kidnapping of 276 girls and young women writing final examinations at a boarding school in the remote northeastern town of Chibok.

Dozens escaped on their own in the first couple of days, but 219 remain missing. Their plight drew protests around the world with demands that the military and government get them free.

The United States, Britain, France and China sent experts to help find the girls, and U.S. drones flew over the area they are believed captive. But Badeh said months ago that they feared a military campaign to free the girls would lead to many of their deaths.

Dozens more schoolgirls and boys, young women and men have been kidnapped by the extremists in a 5-year-old insurgency.

Jonathan told the United Nations last month that the extremists have killed 13,000 civilians.

Hundreds of thousands have been driven from their homes, many of them farmers, causing a food emergency in the northeast of the country where the insurgency is centered.

But Boko Haram has struck elsewhere, with suicide and car bombing attacks in northern cities, in Abuja, the capital in the center of the country, and one failed car bomb in Lagos, the commercial capital in the southwest.

This week, nearly 100 soldiers have been on trial before a court-martial for mutiny and conspiracy to mutiny by refusing to fight the insurgents.

Demoralized troops have told The Associated Press that Boko Haram is better equipped and better armed, and that their officers steal some of their pay. They complain that they are abandoned to fight in the bush with no food or water.

In August, Boko Haram began seizing and holding territory where it declared a caliphate, apparently copying the Islamic State group fighting in Iraq and Syria.

But the tide appears to have turned in recent weeks, with the military wrestling some towns from the extremists and reporting to have killed hundreds of Boko Haram fighters.