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 its fighters, who are 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.
The chief of defence staff, Air Marshal Alex Badeh, announced the truce and ordered his troops to immediately comply with the agreement.
"Already, the terrorists have announced a ceasefire in furtherance of their desire for peace.
"In this regard, the government of Nigeria has, in similar vein, declared a cease-fire," Omeri said.
He confirmed there had been direct negotiations this week about the release of the abducted girls.
Another official said the talks took place in neighbouring Chad. He spoke on condition of anonymity because he is not authorised to talk to reporters.
Some 276 girls were seized from their dormitories at the Government Girls Secondary School in the remote town of Chibok in Borno state, northeastern Nigeria, on the night of April 14.
Fifty-seven escaped and Boko Haram leader Abubakar Shekau later vowed to sell the rest as sex slaves.
Jonathan was criticised at home and abroad for his slow response to the kidnapping and for his inability to quell the violence by the terror group, whose name means "Western education is forbidden".'
The Nigerian military has twice claimed its leader Abubakr Shekau had been killed, but Boko Haram later issued video denials.
The latest one came earlier this month when he was apparently seen in a video that shows the beheading of a man who identifies himself the pilot of a missing Nigerian Air Force jet
Their plight drew global attention, magnified by a #BringBackOurGirls Twitter campaign that drew in celebrities including Michelle Obama and Angelina Jolie.