The terror group made the claim in a new video, said an AFP report.
In the video, the group's leader, Abubakar Shekau also denied claims by Nigerian government that it had agreed to a ceasefire and apparently ruled out future talks.
In another shocking revelation, Shekau said the group have also holding a German national, who was kidnapped in Adamawa state in northeast Nigeria in July.
The schoolgirls were kidnapped from a remote northeast town of Chibok in Borno state in April.
In last five years, the Boko Haram insurgency in northern Nigeria has claimed nearly 13,000 lives.
On October 17, the Nigerian government had made an announcement that a deal had been signed with the militants to end violence in the country and return the girls. However, last week there were reports that the group kidnapped more girls and bombed a bus station in the northern city of Gombe killing at least eight.