"We cannot confirm if the Chibok girls are in this group," it said, adding that Nigerian troops had also destroyed three camps run by the militants.
Diplomats and intelligence officials say they believed at least some of the girls were being held in the forest about 60 miles from Chibok, although U.S. reconnaissance drones failed to find them.
Nigerian forces backed by warplanes invaded the vast former colonial game reserve late last week as part of a push to win back territory from the group.
Boko Haram kidnapped more than 200 schoolgirls near the northern village of Chibok in April 2014, sparking international outcry.
They were taken away in trucks on the night of April 14 to 15, after the terrorists from Boko Haram - meaning 'Western education is sinful' - broke into their school by pretending to be guards.
The students were forced to convert to Islam and marry group members.
The attack sparked worldwide condemnation and a huge campaign called "#bringbackourgirls" - but more than 200 are still missing after others were freed or killed.
Just last week, Nigeria marked the first anniversary since the girls went missing with Nigeria's new president saying he did not know if they would ever be found.
Muhammadu Buhari, who won the presidential election two weeks ago, said his administration would do everything in their power to bring the students home - but said he could not promise they would find them.
The announcement came as a march was held through the Nigerian capital of Abuja to mark the first anniversary since the girls were abducted from a secondary school in Chibok.
"We do not know if the Chibok girls can be rescued," Mr Buhari said.
"Their whereabouts remain unknown. As much as I wish to, I cannot promise that we can find them."
"My government will do everything in its power to bring them home," he added.
Meanwhile, Amnesty International said in a report that Boko Haram has kidnapped at least 2,000 Nigerian women and girls since the start of 2014, many of whom were sexually abused or trained to fight.
However, with help from state neighbours Niger, Cameroon and especially Chad, the rebel Boko Haram force in Nigeria have been forced to retreat from an area the size of Belgium in the last few weeks.
It comes as the group pledged their allegiance to ISIS leader Abu Bakr al-Baghdadi.
Instead they now refer to themselves as Wilayat al Sudan al Gharbi, which is commonly translated into English as the 'West African Province' of the Islamic State.
Since their ISIS allegiance video earlier in the year, Boko Haram has not released any official propaganda photographs or video footage.
- Daily Mail
